Question

x is a consecutive whole number and the first four values of expression x³ + 3y − 3 are 7, 20, 45, 88, then the fifth value is
1. 137
2. 155
3. 158
4. 143
5. None of the above/More than one of the above

Answer 1

Correct Answer - Option 2 : 155

Given:

expression = x³ + 3y − 3

The first four values = 7, 20, 45, 88

x is a consecutive whole number

Calculation:

Let us take x = 1 for first value 7

substitute the value of x in given expression

⇒  1 + 3y − 3 = 7 

⇒ y = 3

For x = 2 (second value)

⇒ 8 + 3y − 3 = 20 

⇒ y = 5

Here x = 1 ,then y = 3 

x = 2 , then y = 5 

so x is increasing by 1 and y is increasing by 2 

Then for x = 5 (Fifth value) , then y = 11

Substitute x = 5 and y = 11 in equation

5³ + 3 × 11 − 3 = 155

∴ The fifth value value is 155