Latest Elitmus Aptitude Question SOLUTION: Q. A digits of a 2 digit no are multiplied,the digits of the product is again multiplied and this process continues untill the number becomes 1 digit number.How many such number

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(#M40031968) ELITMUS Numerical Ability question Multiplication Keep an EYE

Q. A digits of a 2 digit no are multiplied,the digits of the product is again multiplied and this process continues untill the number becomes 1 digit number.How many such numbers are there between 10-99 which have their last result,means the 1 digit number which comes after continuous multiplication of digits, equal to a prime number?

Asked In Elitmus (10 years ago)

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Read Solution (13) :

RAKESH  (10 years ago)

10-19 12,13,15,17(4)
20-29 21,26 (2)
30-39 31,34,35,37 (4)
40-49 43 (1)
50-59 51,53,57 (3)
60-69 62 (1)
70-79 71,73,75 (3)
80-89 & 90-99 none
total=4+2+4+1+3+1+3=18

Is this solution Helpfull? Yes (16) | No   

parul  (10 years ago)

27 is nt in option..28 is the answer..as we know single digit prime no is 2 3 5 7
so scanning 11=1, 12=2 13=3 14=4 15=5 16=6 17=7 18=8 19=9 20=2 (5 prime no)
similarly 21=2 22=4 23=6 24=8 25=1 26=2 27=4 28=6 29=8 30=3 (3 prime no)
31=3 32=6 33=9 34=2 35=5 36=8 39=4 40=4(3 prime no).41=4 42=8 43=2 44=6 45=2 46=8 47=6 48=6 49=8 50=5(3 prime no) 51=5 52=1 53=5 54=2 55=1 56=3 57=5 58=4 59=2 60=6(6 prime no) 61=6 62=2 63=8 64=8 65=3 66=8 67=8 68=6 69=2 70=7(4 prime no)71=7 72=4 73=2 74=6 75=5 76=8 77=8 78=3 79=8 80=8(4 prime no) 81=8 82=6 83=8
84=6 85=4 86=6 87=3 88=8 89=4 90=9(1 prime no) 91=9 92=8 93=4 94=8 95=2 96=2 97=8 98=4 99=8(2prime no)

Is this solution Helpfull? Yes (3) | No   

prerna  (10 years ago)

18 is the answer

Is this solution Helpfull? Yes (2) | No   

Sona  (10 years ago)

Prime numbers are 2,3,5,7.
To get 2 as the last digit:
21== 2*1=2
but u can also split 21 as 37== 3*7=21 == 1*2=2
similarly 73
12== 1*2=2
similar to abv: 12 is split as 6*2 == 62
and thus even 26,43,34

so for 2:12,26,62,43,34,21,37,73
to get 3: 13 and 31
to get 5: 15,35,53,51,75,57
for 7: 17,71

ans is 18.

Is this solution Helpfull? Yes (2) | No   

amit choudhary  (10 years ago)

@parul,gr8 work girl...

Is this solution Helpfull? Yes (1) | No   

kuldeep kushwaha  (10 years ago)

Ans is 27.,.,.anybody rem the other option

Is this solution Helpfull? Yes | No (2)  

amit choudhary  (10 years ago)

Could you please explain it ?

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rohitashwa  (10 years ago)

@parul 55=5*5=25=5*2=10=1*0=0....(n u have taken as 1..)aren't u splendid..heheheh srry stupid..(lolz..

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rohitashwa  (10 years ago)

@parul tune to 20, 30, 40,50 52 sabhi le rakha hai al of dem are 0 n 0 nt a prime no..

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amit choudhary  (10 years ago)

@ROHITASHWA leave tht bro...@Parul improve your answer..

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Vijay Singh Adhikari  (10 years ago)

11,12,13,15,17,21,31,51,71
ans is 9 .....correct me if i am wrong

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Vijay Singh Adhikari  (10 years ago)

@ rakesh ..u r genius bro...most of ur r correct with clear explaination ..it really helps a lot..

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Arti Soni  (10 years ago)

10-19 11,12,13,15,17(5)
20-29 21,26(2)
30-39 31,34,35,37(4)
40-49 43(1)
50-59 51,53,57(3)
60-69 62(1)
70-79 71,73,75(3)

total=5+2+4+1+3+1+3=19

Is this solution Helpfull? Yes | No (2)  

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