Number Analogy 1
Q) 15 : 63 :: ? : 255
Trick
Observe: i. 15 = 16 − 1 = 4² − 1, ii. 63 = 64 − 1 = 8² − 1
Base doubles: 4 → 8
Now, 255 = 256 − 1 = 16² − 1
So the missing number should be: 12² − 1 = 144 − 1 = 143
Thus, 15 : 63 :: 143 : 255
Ans: (A) 143
Q) 15 : 63 :: ? : 255
Trick
Observe: i. 15 = 16 − 1 = 4² − 1, ii. 63 = 64 − 1 = 8² − 1
Base doubles: 4 → 8
Now, 255 = 256 − 1 = 16² − 1
So the missing number should be: 12² − 1 = 144 − 1 = 143
Thus, 15 : 63 :: 143 : 255
Ans: (A) 143