Select the option that is related to the third number in the same way as the second number is related to the first number.
400 : 20 :: 100 : ?

Correct option is B

The relationship between the first pair of numbers 400 : 20 :: 100 : ? is:
400÷20= 20
To apply the same relationship to the second pair:
100÷?=10
Rewriting:
?=100÷10=10
Thus, the number related to 100 is 10.