Problems on Numbers · Exercise 4 of 6
65 mixed-level problems on numbers in the style of campus placement tests (TCS, Infosys, Wipro, Accenture, Cognizant, Capgemini), SSC CGL/CHSL/MTS, RRB NTPC and Group D, IBPS/SBI, UPSC CSAT and state exams.
If x/3 + x/4 + x/6 = 18, what is x?
LCM of 3, 4, 6 is 12
4x/12 + 3x/12 + 2x/12 = 9x/12 = 18
x = 24
Answer: 24
A three-digit number is formed by writing the same digit three times (such as 444). Every such number is exactly divisible by:
aaa = a × 111
111 = 3 × 37
So every such number is divisible by 37 (and by 3)
Answer: 37
For how many integers from 1 to 100 is the number equal to 4 times the sum of its digits?
Single-digit numbers cannot work (d = 4d only for 0).
Two-digit: 10a + b = 4(a + b) → 6a = 3b → b = 2a
a = 1 to 4 → 12, 24, 36, 48
100 does not work
Count = 4
Answer: 4
A number is subtracted from 50 and the result is multiplied by 3 to give 66. What is the number?
3(50 − x) = 66
50 − x = 22
x = 28
Answer: 28
Two numbers add up to 96, and one-fifth of the larger equals one-third of the smaller. What is the larger number?
L/5 = S/3 → L : S = 5 : 3
Larger = 96 × 5/8 = 60
Answer: 60
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