Question

The average of 35 results is 30; the average of the first 17 results is 21 and that of the last 17 results is 25 then what is the 18th result?
1. 268
2. 384
3. 245
4. 254

Answer 1

Correct Answer - Option 1 : 268

Given:

The average 35 results = 30

The average first 17 results = 21 

The average last 17 results = 25 

Formula used:

Average = Sum of all observations/Total number of observation

Sum of all observations = Average × Total number of observation 

Calculation

Sum of 35 results = 35 × 30 = 1050

Sum of 17 results = 17 × 21 = 357

Sum of 17 results = 17 × 25 = 425

According to the question,

= 35 × 30 – 17 × 21 – 17 × 25

⇒ 1050 – 357 – 425

⇒ 1050 - 782 = 268

∴ The 18th result will be 268.