Elitmus
Exam
Logical Reasoning
Number Series
Find the number of zeros in the product:
1^1*2*2*3^3*4^4............98^98*99^99*100^100
A)1200
B)1300
C)1050
D)None of these
Read Solution (Total 14)
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- B) 1300
Number of zeroes will depend on number of multiplication by 10 in the given expression
Also, 10=2*5
Obviously there will be more 2's than 5's in the expression
So we have to only fint the number of 5 in the given expression which if given by the numbers whose last digit it either 0 or 5:
like 5^5 contains 5 '5's
10^10 contains 10 '5's
hence:
5^5 - 05
10^10 - 10
15^15 - 15
20^20 - 20
25^25 - 2*25=50 (as 25=5*5 contains two 5's)
30^30 - 30
35^35 - 35
40^40 - 40
45^45 - 45
50^50 - 100 (50=5*5*2)
55^55 - 55
60^60 - 60
65^65 - 65
70^70 - 70
75^75 - 150 (75=5*5*3)
80^80 - 80
85^85 - 85
90^90 - 90
95^95 - 95
100^100 - 200 (100=5*5*4)
Hence total number of 5's= 5+10+15+20+50+30+35+40+45+100+55+60+65+70+150+80+85+90+95+200=1300 - 11 years agoHelpfull: Yes(38) No(1)
- calculate powers of 5 & multiple of 5...
5+10+15+.......+100= 1050
since in 25,50,75&100 contains 5^2
so their respective powers should be added one more time
25+50+75+100=250
total=1050+250=1300 ans. - 11 years agoHelpfull: Yes(28) No(1)
- is ter anyone here who can help me out in elitmus test i've my test on this sunday... 7th of july...
- 11 years agoHelpfull: Yes(7) No(0)
- the answer 1300 seems to be correct.If so, the answer given in book arun sharma i.e. 1050 is wrong
- 11 years agoHelpfull: Yes(4) No(0)
- me too friends aravind.mitra6@gmail.com send me all types of meterial u have abt Elitmus Questions
- 11 years agoHelpfull: Yes(1) No(0)
- the answer 1300 is correct and the answer given in arun sharma is also 1300
- 11 years agoHelpfull: Yes(1) No(0)
- the smallest no. that contains 0 is 10
10=5*2 so just calculate no of 5 in the given expression
the no that contain 5 are {5,10,15,20......}
so taking this no only we have 5^5*10^10*.....100^100= ( 5^5*5^10*5^15....)=5^1050 - 11 years agoHelpfull: Yes(0) No(3)
- The answer is 1050
- 11 years agoHelpfull: Yes(0) No(3)
- mr.sumit pls expln d answer?
- 11 years agoHelpfull: Yes(0) No(2)
- I m having elitmus exam on nxt sunday...plz mail me all questions at shwetashrm.991@gmail.com
- 11 years agoHelpfull: Yes(0) No(0)
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- I m having elitmus exam on nxt sunday...plz mail me all questions and any study material at neetigupta.bu@gmail.com............plz plz its urgent........
- 11 years agoHelpfull: Yes(0) No(0)
- @arpit pls explain me the details abt '25^25'-50 ...pls pls...
- 11 years agoHelpfull: Yes(0) No(1)
- Answer will be 1050..
since we need to count only nos of 5
so count no. of 5 is 5^5+10^10+15^15+20^20.....100^100
that will be 5+10+15+20+25+30......100 = 1050 - 11 years agoHelpfull: Yes(0) No(6)
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