A number leaves remainder 3 when divided by 7 and remainder 3 when divided by 5. The smallest such number above 3 is:
A33
B38
C35
D31
Answer & Solution
Correct answer: B. 38
1. If a number leaves the same remainder 3 with both divisors, then the number minus 3 is divisible by both.
2. So the number minus 3 must be a common multiple of 7 and 5.
3. Since 7 and 5 share no prime factor, their LCM is 7 x 5 = 35.
4. The smallest such value above 3 is therefore 35 + 3 = 38.
5. 33 and 31 are not 3 more than a multiple of 35, and 35 itself leaves remainder 0 with 5.
_Source: syllabus Maths, Ch 1 'Real Numbers', S1.2 The Fundamental Theorem of Arithmetic_
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