A circular disc of area 0.49*Pi square metres rolls down a length of 1.76 Km. The number of revolutions it makes is

M4maths Previous Puzzles

13 Nov 2014 Area A circular disc of area 0.49*Pi square metres rolls down a length of 1.76 Km. The number of revolutions it makes is: OPtion
1) 300
2) 200
3) 400
4) 500
5) 600
6) 1600
7) 3000
8) 4000
9) 1400
10)None of these; Correct Option: 3 Best Solution (88)

MAHARAJAN.G 10 years AGO

area=pi*r^2=0.49*pi => r^2=0.49 => r=0.7
radius=r=0.7 diameter=r*2=0.7*2=1.4
in here if a disc rotates it moves certain distance that distance is measured as length of disc rotates so
length of disc is=pi*d=distance moved by disc (one revolution)=pi*d=3.14*1.4=4.396
total distance=1.76km=1760m
total revolution=total length crossed/length of one revolution
total revolution=1760/4.396=400

Like? Yes (4) | No (1)

LOKESH KUMAR 10 years AGO

Area=.49*pi
= radius(r)=.7
=circumference(c)=2*pi*.7
=Total length(l)=1.76*1000=1760
=Number of revolutions=l/c
=(1760)/(2*pi*.7)
=400

Like? Yes (3) | No

Anand 10 years AGO

pi *r^2=0.49 pi

r=7/10
circumfrence= 2*pi*7/10
=44/10
no of revolution= 1.76*1000*10/40

Like? Yes (3) | No (1)

Deepak prajapati 10 years AGO

n*(2*pi*r)=1760
by given area we can calculate radius =.7
so n=400

Like? Yes (2) | No

prem kumar chaudhary 10 years AGO

2*pi*r*n=1.76*1000
r=0.7
n=400

Like? Yes (2) | No

bikash tiwari 10 years AGO

1.76*10^3/4.396=400.363

Like? Yes (2) | No

Sravanthi 10 years AGO

Radius=7/10
circumference=2*(22/7)*(7/10)=44/10
number of revolutions=1.76*1000*(10/44)=400

Like? Yes (3) | No (1)

Gaurav Sharan 10 years AGO

r= 0.7
1.76*1000=(n)*2*(22/7)*0.7
gives n = 400

Like? Yes (2) | No

pravin 10 years AGO

pi*r^2=0.49pi
r=0.7m
circumference=2*pi*r=440m
no. of revolution=(1.76*1000)/440=400

Like? Yes (2) | No

Chirag Ranjan Lahiri 10 years AGO

2*pi*r = 2*3.14*0.7 = 4.398m

so, ans will be 1760/4.398 = 400 answer......

Like? Yes (2) | No

Udhaya kumar 10 years AGO

pi * r^2 = 0.49 pi
r = 0.7
2 * pi * r = 4.4
1760 / 4.4 = 400.....

Like? Yes (2) | No (1)

ravi prakash 10 years AGO

17600/44

Like? Yes (1) | No

Arijit Das 10 years AGO

Area of the circular disc= pi*r2= 0.49*pi
therefore, r= 0.7 m
Perimeter of the circular disc = 2*pi*r =2*pi*0.7
=4.39823 m
No. of revolutions it will make= DISTANCE/PEREMETER
=(1.76*1000)/4.39823
=400

Like? Yes (2) | No (1)

ranjithreddy 10 years AGO

r=0.7meters.
circumfernce+=2*pi*0.7=4.4metres.
no Of revolutions=1.76*1000/4.4=400

Like? Yes (1) | No

MINTU KUMAR GUPTA 10 years AGO

pi*r^2=0.49*pi
r=0.7m
no of revolution=1.76*1000/(2*pi*0.7)
=400

Like? Yes (2) | No (1)

Ajinkya Kulkarni 10 years AGO

No of revolution equals to distance divided by perimeter...
1760/(2π*0.7)=400

Like? Yes (1) | No

Divyank Dubey 10 years AGO

area of circular disc = pi*R^2=.49*pi (given)
so, R=0.7
And distance traveled by disc in 1 revolution=2*pi*R
so if n revolution takes to travel distance=1.76KM
== 1.76*1000=(2*pi*0.7)*n
== n=400

Like? Yes (1) | No

Rishikesh Ranjan 10 years AGO

r=0.7
no of revolsn=1.76*1000/2pi*.7= 400

Like? Yes (1) | No

aman 10 years AGO

0.49pi=pi r^2
r=7/10
Circumference =2 pi*r
44/10

Revolution = length in meter/circumference
(1.76*1000)/(44/10) =400

Like? Yes (1) | No

ARJUN PRASAD 10 years AGO

pi*r^2=pi*0.49
r=0.7
circumference=2*pi*r=1.4*pi
no. of revolution=(1.76*1000)/1.4*pi=400 approx.

Like? Yes (2) | No (1)

Jabez David 10 years AGO

circular disc of area 0.49*Pi

Pi*R^2=0.49*Pi
R=7/10 m

Circumference= 2*pi*R
=44/10 m

number of revolutions = 1.76*1000*44/10
= 400

Option 3

Like? Yes (1) | No

Ramrup Chatterjee 10 years AGO

n*2*3.14*.7=1760
so n=400

Like? Yes (2) | No (1)

abhishek narayan 10 years AGO

area=pi*r^2=0.49*pi
r=0.7
circumference=2*pi*0.7=1.4*pi
no. of turns= (1.76*1000)/(1.4*pi)=400

Like? Yes (1) | No

Dinesh thatti 10 years AGO

pi r^2=0.49pi = > 49pi/100 * 1/pi = > r =7/10 m
Circumference= 2pir => 2* 22/7* 7/10 =44/10 m

no of revolutions= 1.76*1000*44/10=400

Like? Yes (1) | No

kamal 10 years AGO

pi*R^2=.49*pi
R^2=.49
R=.7
so circumference = 2* pi * .7=4.4
no of revolution= 1.76* 1000 * 1/4.4=400.

Like? Yes (1) | No

vikash kumar 10 years AGO

1.76*1000/(3.14*1.4)=400.36=400

Like? Yes (1) | No

Arijit Acharyya 10 years AGO

pi*r^2 = 0.49*pi
r=0.7
2*pi*r = 2*(22/7)*0.7 = 4.4 m
1.76 km = 1,760 m
the number of revolution it makes = 1,760/4.4 =400 revolutions

Like? Yes (1) | No

SHIVAM KASHYAP 10 years AGO

radius =7/10,1 revolution=(2*22*7)/7000

Like? Yes (1) | No

pawan kumar 10 years AGO

radius= 0.7 m
so, perimeter = 22/5 m

hence,
No. of revolution= (1760*22) / 5
= 400

Like? Yes (1) | No

jagan 10 years AGO

area of disc=.49*pi so r=.7mtr
perimeter of circle=2*pi*r=2(22/7)*.7=4.4mtr
required distance=1.76km=1760mtr
so revolutions=1760/(4.4)=400

Like? Yes (1) | No

anuj gupta 10 years AGO

400

Like? Yes (1) | No

gouthamdaneti 10 years AGO

let n be the number of revolutions
1.76 = n*2*.7*Pi/(1000)

Like? Yes (1) | No

RAMAKRISHNA 10 years AGO

pi*r^2 =0.49 *pi r=0.7 m
circumference=2*Pi*r
n0. of revolutions =1.76*1000*10/44=400

Like? Yes (1) | No

rahul ranjan 10 years AGO

pi*r2= .49pi
r=.7
circumference=2pi*r=4.4m
no of rool = 1.76km/4.4m= 400

Like? Yes (1) | No

Chandra chur anand 10 years AGO

pi*r^2=0.49pi
so r=7/10m
now circumference= 2*pi*7/10=2*22/7*7/10
=44/10m
so no. of revolution=1.76*1000*10/44 revolution
=400 revolution...ans

Like? Yes (1) | No

T.Aravinth kumar 10 years AGO

r=0.7
1.76*10^3/2pi*r=400

Like? Yes (1) | No

AMREEN 10 years AGO

Area =0.49*Pi
pi*r*r=0.49*pi
r*r=0.49
r=0.7m
let no. of revolution=n
perimeter*n=1.76*1000 m
2*pi*r*n=1.76*1000m
n=400

Like? Yes (1) | No

aman 10 years AGO

find r, then find circumference then divide it by 1760

Like? Yes (1) | No

Manjesh 10 years AGO

area = pi *r*r which is equal to .49pi sq. mts
therefore, r=.7
circumfrence =2*pi*r
no of rev= (total length covered /circumfrence)
i.e
17600/(2*pi*.7)=400

Like? Yes (1) | No

Shivan kumar jha 10 years AGO

3.14*049=3014*0.7*0.7'
r=0.7
so,2*3.14*0.7=(22/5 m area will cover in one round)
1.76*1000(convrt into metre)=1760*5/22=400
option:3(400)

Like? Yes (1) | No

Manoj Chouhan 10 years AGO

Area πr2 = 0.49*π
r2 =0.49
r = 0.7

One circle of disc will be equal to the circumference.

now, circumference C = 2πr
C = 2*3.14*0.7
C = 4.398 or 4.40

if it has to complete 1.76 km, than divide it ...
1 circle = 1.76 km/4.40
1 circle = 176000 meter/440
= 400 ans (3)

Like? Yes (1) | No

satyam sharma 10 years AGO

1760/(2*pi*0.7)=400
so correct option is 3

Like? Yes (1) | No

Vandana Sahu 10 years AGO

1.76*1000/2*.7*pi

Like? Yes (1) | No

himasnhu joshi 10 years AGO

area =.49*pie
pie*r^2=.49*pie
r=.7
circumference=2*pie*r=2*3.14*.7=4.38m
1 revolution=4.38m
400=1.76km
ans =400
i.e 3)400

Like? Yes (1) | No

Neha Pandey 10 years AGO

no. of revolutions= total distance/ perimeter of the disc.
perimeter = 2*pi*r
area= pi*r*r
r= 0.7
so, perimeter = 4.4 m

Like? Yes (1) | No

Manav singh 10 years AGO

r=7/10. then circumference=22/5. now no. rolls= 1760*5/22 gives 400

Like? Yes (1) | No

A M ANKIT KALLURAYA 10 years AGO

N=1.76/(pi*.49)

Like? Yes (1) | No

Mani Shankar 10 years AGO

0.49*pi = 2*pi*r^2
so, r = 0.7
thus 2*pi*r * x = 1.76 km = 1760 m
so x = 400

Like? Yes (1) | No

RAJEEV RANJAN 10 years AGO

(1.76*10^3)/(2*pi*.7)=
=400

Like? Yes (1) | No

RAKESH 10 years AGO

A = 0.49*Pi m^2 => r = .7m

C = 2*pi* .7 = 4.4m

no. of revo = 1760m / 4.4 = 400 ..........

Like? Yes (1) | No (1)

Anand Dwivedi 10 years AGO

49/100*pi*1/*= 7/10
2*pi*7/10=44/10
no of revolution = 1.76*1000*10/44=400

Like? Yes (1) | No (1)

padmaja 10 years AGO

Area=PI*R^2
0.49*Pi =Pi*R^2
R=0.7m or 7/10 m
Circumference=2*Pi*R
=2*(22/7)*(7/10)
=4.4m or 44/10 m
Number of revolutions=1.76*1000*(10/44)
=400

Like? Yes (1) | No (1)

v pavan 10 years AGO

area=pi*r^2=0.49*pi
solving we get r=0.7
1revolution=2*pi*r
no. of revolutions= 1760/(2*pi*0.7)=400

Like? Yes (1) | No (1)

Maniratnam 10 years AGO

pi*r^2 = 0.49*pi from this r = 0.7 m, 1 Rev = 4.4 m then 1.76 km = 1760/4.4 there fore 400 revs

Like? Yes (1) | No (1)

swarupa nuggu 10 years AGO

Like? Yes (1) | No (1)

Manasa Dullur 10 years AGO

Pi * r^2 = .49 Pi = > r = .7,
2Pi* .7*k = 1.76 * 1000, k = 400

Like? Yes (1) | No (1)

kancharla kavya 10 years AGO

Given area of circular disc is 0.49*pi Sqmts....
so.., pi*r^2 =0.49*pi ;
r^2=0.49;
r=0.7 mts;
Circumference of a circle which makes n revolutions=length it has roll down;
so...2*pi*r*n=l;
Given l=1.76 km;
=1.76/1000
=1760 mts;
Now n= l/(2*pi*r)
=1760/(2*(22/7)*0.7)
=1760/(22/5)
=(1760*5)/22
=400
so number of revolutions is 400....

Like? Yes (1) | No (1)

SUBHASH TULSYAN 10 years AGO

pie*r*r=0.49*pie
so r=0.7 m
no. of revolution=(1.76*1000)/(2*pie*0.7)
=400.16
=400 (approx)

Like? Yes (1) | No (1)

Akshay 10 years AGO

pi*r*r=0.49*pi
r=0.7
circumference=2*pi*r=4.4meter
number of revolution=1760/4.4=400

Like? Yes (1) | No (1)

Md.Sultan Khichi 10 years AGO

Area of circle=.49π
πr^2=.49π
r=.7m
Circumference=2*22/7*.7=4.4m
Revolution=1.76*1000/4.4=400
Ans. On 3

Like? Yes (1) | No (1)

Parag Wagh 10 years AGO

r=0.7
2*pi*r=4.39
1760/4.39=400

Like? Yes (1) | No (1)

Abhishek mani 10 years AGO

pi*radius^2=0.49pi*pi sq metre
so,r=0.7
so.circummference=2*pi*r
(1760/2*pi*0.7)
=400

Like? Yes (1) | No (1)

vaitesh mudaliar 10 years AGO

area = pi*r^2 = 0.49pi so,r= 0.7 m. circumference =2*pi*r ,
length traveled =1760 m.
no. of revolutions = 1760/2*pi*r = 400 revolutions

Like? Yes (1) | No (1)

subhadeep santra 10 years AGO

pi*r^2=.49*pi=>r=.7;Let n be the no. of revolution .
n*2*pi*r=1.76*1000=>n=400.

Like? Yes (1) | No (1)

Swagatam Kumar Das 10 years AGO

22/7*R^2=.49*pi
so R is .7
So no of revolutin is1.76*1000/2*pi*.7 =400

Like? Yes (1) | No (1)

Deb Das 10 years AGO

17600/(2*22/7*7)=400

Like? Yes (1) | No (1)

Souvik Adhikary 10 years AGO

Pi*r^2=0.49*Pi
r=0.7
2*Pi*r=4.4
no. of revolution =1760/4.4=400

Like? Yes (1) | No (1)

Jayanta Dutta 10 years AGO

Pi*R^2=.49*Pi
or,R=7/10;

Circumference =2*22/7*7/10;

=44/10;

so revolutions= 1.76*100*10/44

=ans(3) 400

Like? Yes (1) | No (1)

A SIRISHA 10 years AGO

AREA OF CIRCULAR DISC = Pi*r^2 = Pi*0.49
=Pi*(0.7)^2
so, radius r = 0.7
Distance covered in 1 revolution=circumference =2*Pi*r
= 2*(22/7)*0.7
=4.4m
so no.of revolutions= (1.76*1000)/4.4
=400

Like? Yes (1) | No (1)

Payal Namdeo 10 years AGO

In 1 revolution=2πr=2*π*0.7=22/5m
No. Of revolution =1760*5/22=400

Like? Yes (1) | No (1)

sanjeev kumar 10 years AGO

ans 400

Like? Yes (1) | No (1)

niraj 10 years AGO

1760/4.396=400.02

Like? Yes (1) | No (1)

Ramesh Sriram 10 years AGO

PI*r2=0.49PI
Number of rolls=(1.76*10000*7)/(2*22*0.7)
=400

Like? Yes (1) | No (1)

suparna senapati 10 years AGO

pi*r(square)=0.49*pi
r=7/10
circumference=2*pi*r=44/10m
number of revolution=1,76*1000*10/44=400

Like? Yes (1) | No (1)

NAVEEN KUMAR 10 years AGO

perimeter of circular disc=2*pi*0.7=4.4m

The number of revolutions=1760/4.4=400 option(3)

Like? Yes (1) | No (1)

Aparna Chakraborty 10 years AGO

pi*r^2 = .49m^2
r= 0.7 m
2pi*r= 4.4m = .0044km
revolutions= 1.76/.0044
=400

Like? Yes (2) | No (2)

madanpal vishwakarma 10 years AGO

given area of disk= 0.49*pi
so radius of disk =0.7
so circumference of disk= 2*pi*0.7= 4.396(approx)

so to cover 1.7km= 1760m the disk have to revolve =1760/4.396= 400 round

so option 3 is correct

Like? Yes (1) | No (1)

Shashi nath jha 10 years AGO

ans-400

Like? Yes (1) | No (1)

pritam banerjee 10 years AGO

pir^2=.49pi so r=.7 so rev=1760/2*pi*.7

Like? Yes (1) | No (1)

BHASKAR MANDAL 10 years AGO

answer is 400

Like? Yes (1) | No (1)

kiran chillerge 10 years AGO

w.k.t area=pi*r*r
hence r=0.7
now circumference=2*pi*r
therefore total revolutions=distance covered/circumference
=1.76*1000(in metres)/(2*.7*3.142)
=400(approx)

Like? Yes (1) | No (1)

Aparna Bhattacharya 10 years AGO

pi*R^2=0.49*pi
R^2=(49*pi/100)*(1/pi)
R=7/10 m
Circumference=(2 * 22/7 * 7/10)m=44/10 m
Number of revolutions=1.76 * 1000 * 10/44=400
Option: 3

Like? Yes (1) | No (1)

Tark Patel 10 years AGO

Circular disk area = 0.49*pi then

radius = 0.7

2*pi*radius = 1 revolutions

then for 1.76 km total number of
revolutions are = (1.76 * 1000) / (2*pi*0.7) = 400

Like? Yes (1) | No (1)

CHANDAN KUMAR 10 years AGO

pi*r^2=0.49pi
r=0.7
c=1.4*pi
rev=1760/1.4*pi=400

Like? Yes (1) | No (1)

Bimal Behera 10 years AGO

circular disc area=pi*r^2
so r=root of 0.49=0.7
then perimeter=28pi*r=2*3.14*0.7=4.4meter
total revolution=(1.76*1000)/(4.4)=400

Like? Yes (1) | No (1)

ayushi 10 years AGO

since area =0.49 * pi sq m
=> 0.49*pi=pi*r*r;
=> r=0.7
=> perimeter=2*pi*r;
=> =4.396 m;
=> no of revolutions=1.736*1000 m/4.396m;
=> =394.90=400(appro)

Like? Yes (1) | No (1)

Surit Datta 10 years AGO

according to the problem
π*R*R = 0.49 *π
so R = 7/10 m
so circumference = 2* π*R = 44/10 m
so no of revolutions = (1.76*1000*10)/44 = 400
That's it.

Like? Yes (1) | No (2)

Anoop Tiwari 10 years AGO

pi*R*R=0.49Pi
R*R=(49pi/100)*(1/pi)
R=7/10
circuumference=2*pi*R=2*22/7**7/10=44/10
no. of revolutions=L/2pi*R=1.76*1000/44/10=1.76*1000*10/44
=400
hence option 3) is correct

Like? Yes (1) | No (2)

Dimple

India

Punjab

Time: 00:01:33

Points

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A circular disc of area 0.49*Pi square metres rolls down a length of 1.76 Km. The number of revoluti

M4maths Previous Puzzles

13 Nov 2014 Area