Elitmus
Exam
Numerical Ability
Number System
A maximum number of 3 digit such that when expressedin base 2 or base 3 or base 7 has 1 as the rightmost(last) digit. If a,b,c are the first digits(leftmost) of the base 2, base 3 and base 7 representation of that number. Then sum of a,b,c
Read Solution (Total 9)
-
- given that right most digit is 1.
means in base system 1 is remainder in each case.
we have to find greatest 3 digit number, so first we have
to find the greatest 3 digit number which is divisible by 2,3
and 7.
so take lcm of 2,3 and 7.
LCM(2,3,7)=42.
Now
42)999(23
84
-----
159
126
-------
33
so greatest 3 digit number which is divisible by 2,3 and 7 is
999-33=966
Number which have right most digit is 1 is equal to 966+1=967.
now express this number in base 2, base 3 and base 7 system
and find a,b and c.
- 10 years agoHelpfull: Yes(9) No(0)
- a=1 , b=1 , c=2 ans is 4
number is 967 - 10 years agoHelpfull: Yes(4) No(0)
- The number is 967, 2*3*7 = 42, highest 3 digit number = 42*23 = 966 , 966 +1 = 967
Leftmost digit = 2+1+1 = 4 - 10 years agoHelpfull: Yes(3) No(0)
- 2a+1 = 3b+1 = 7c +1
2a=3b
a=3, b=2 : 7
a=6, b=4 : 13
6p + 7
6p + 7 = 7c + 1
6p + 6 = 7c
6 (p+1) / 7 = c
p=6 : 43
p=13 : 85
42d + 43
42(22) + 43 = 967
967 in base 2 = 1111000111
967 in base 3 = 1022211
967 is base 7 = 2551
answer = 1+1+2 = 4 - 10 years agoHelpfull: Yes(3) No(0)
- The answer is 4
The question says that the number has last digit as 1 in base 2,3,and 7.
You will see that this true for only those numbers which when divided by 2,3,and 7 leaves remainder 1.
So the number will be of format (L.C.M of 2,3,7)*n+1.=42n+1
The highest 3 digit number is 42*23+1=967.
When you will convert it into base 2,3,and 7 the sum of first digit ie a+b+c will be 4
Thanks
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