Question

Find the smallest number which when increased by 11 is exactltly divisible by 15,20,54

Answer 1

15=5×3

20=5×2×2

54=3×3×3×2

Take the most common factors

5×3×3×3×2×2

=540

Now let the number be x

$\frac{x + 11}{540} = 1 \\ \\ x + 11 = 540 \\ \\ x = 529$

Therefore the number is 529

hope it helps