M4maths Previous Puzzles

05 Apr 2016 First negative term

Which tern of the series 27, 24, 21, 18, 15, ..... is the first negative term.

OPtion

1) 9
2) 7
3) 16
4) 11
5) 15
6) 14
7) 10
8) 13
9) 12
10)8

Solution

Here a = 27 and d = 24-27 = -3 (Series is AP)
Let nth tern of the given AP be the first negative tern
Then Tn < 0
=> (a + (n-1)d) < 0
=> (27 + (n-1)(-3)) < 0
=> (27 - 3n + 3) < 0
=> 30 - 3n < =
30 < 3n
3n > 30
n > 10
Therefore n = 11
Hence, the 11th tern is the first negative tern of the give AP.
Option 4)

Correct Option: 4 Best Solution (17)

Mukund Manohar   9 years AGO

The difference in every number d=-3
11th term = 27 +(11-1)*(-3)
=27-30
=-3
So 11th term is the first negative term

Like? Yes (3) | No (1)  

RAHUL KUMAR   9 years AGO

As the first negative number of the series is -3
so there are 11 term from 27 to -3.
Option (4) is the ans.

Like? Yes (1) | No (1)  

dev   9 years AGO

27, 24, 21, 18, 15, 12, 9, 6, 3, 0, -3

so 11th term is the first negative number. so option (4)

Like? Yes (4) | No (4)  

Karthik   9 years AGO

27,24,21,18,15,12,9,6,3,0,-3,....
-3 is the first negative term.
It is at 11th position.

Like? Yes (2) | No (2)  

soundarya   9 years AGO

considering 0 as the last term, applying the formula, of A.P
n=[(l-a)/d]+1, where l=0; a=27;d=-3,
we get n=10;
therefore the first negative term would be the 11th term.

Like? Yes (2) | No (2)  

tasho k   9 years AGO

suppose it is nth term
first neg term will be -3.
by using arithmetic progression
27=-3+(n-1)*3
solving this n=11

Like? Yes (1) | No (2)  

Priya Verma   9 years AGO

the first negative term will be -3 which is 11th term of the series ( difference between the terms of the series is 3)

Like? Yes (1) | No (2)  

CHANDAN KUMAR   9 years AGO

27,24,21,18,15,12,9,6,3,0,-3
so , 11th term is first negative term.
correct options is 4) 11

Like? Yes (1) | No (2)  

ABHINAV PUSHPAM   9 years AGO

The series is a AP with negative common difference (-3) , first term, i.e a=27, and d= -3.
let An be the first negative term.
then, An

Like? Yes (4) | No (8)  

Meenakshi   9 years AGO

In the given A.P series a=27 d= -3
Let n be the first negative term then
27+(n-1)(-3) < 0
30-3n

Like? Yes | No (4)  

SANTOSH KUMAR DASH   9 years AGO

27 =1st term
24=2nd erm
.
.
.
.
.
.
-3=11therm

Like? Yes | No (4)  

aayushi tomar   9 years AGO

a=27,d=-3
so 0=27+(n-1)-3
n=10,so first negative term will be -3 n it will b 11th term

Like? Yes | No (4)  

HARIBASKAR   9 years AGO

27
24
21
18
15
12
9
6
3
0
-3


term = 11

Like? Yes (1) | No (5)  

viswambher   9 years AGO

every term in the series is being reduced by 3 so the series is
27 24 21 18 15 12 9 6 3 0 -3
and the 1st negative term is -3 which is also the 11th term in the series

Like? Yes | No (5)  

Anee Verma   9 years AGO

x = a + (n-1) d
x = no. in series
a = 1st no. in series
n = sequence no. of x in series
d = difference between 2 nos in the series
In our question,
x = -3 (because it -3 will be the first negative no. as all nos are decreasing by 3)
a = 27
n = n
d = -3

Solving the equation, gives n = 11

Like? Yes (1) | No (6)  

Dinesh kumar sah   9 years AGO

In the given series 1st negative number is -3 and if we count the number of terms up to this -3,then there are 11 terms in the above series . So option (4) is the right answer.

Like? Yes | No (5)  

THUMMALA VINEESHA   9 years AGO

27+(n-1)*(-3)30
n>10
so n=11
option 4

Like? Yes | No (5)