Question

If Mean of a, a + 3, a + 6, a + 9 and a + 12 is 10, then a is equal to;
1. 1
2. 2
3. 3
4. 4

Answer 1

Correct Answer - Option 4 : 4

Given:

Observations = a, a + 3, a + 6, a + 9 and a + 12.

Mean = 10

Formula used: 

Mean(a) = sum of observations/number of observations

Calculation:

According to the question, 

Mean(a) = sum of observations/number of observations

⇒ (a + a+ 3 + a + 6 + a + 9 + a + 12)/5 = 10

⇒ (5a + 30)/5 = 10

⇒ 5(a + 6)/5 = 10

⇒ a + 6 = 10

⇒ a = 4

∴  a is equal to 4.