Bunuel wrote:
If n is a positive integer less than 400, what is the number of n such that when n is divided by 4, the remainder is 3 and when n is divided by 7, the remainder is 1?
A. 10
B. 12
C. 13
D. 14
E. 15
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n = 4a+3 = {3, 7, 11,15 , 19, 23, 27, 31, ...}
also
n = 7b+1 = {1, 8,15 , 22, 29, 36, ...}
First common term = 15
Every terms after the first term will be at a gap of LCM (4 & 7) i.e. 28
Terms are {15, 43, 71....}
Last term = 15 + (n-1)*28 < 400
i.e. n-1 < 13.75
i.e. n < 14.75
i.e.
...
