Insert the missing number. 16, 33, 65, 131, 261, (....)

523

521

613

721

Correct Answer : A

A sequence of 4 digits, when considered as a number in base 10 is four times the number it represents in base 6. What is the sum of the digits of the sequence?

PAIN:SEDATIVE

Look at this series: 36, 34, 30, 28, 24, ... What number should come next?