The average of 13 natural numbers is 59. The average of the first 7 natural numbers is 43, and the average of the last 7 natural numbers is 73. Find the seventh number.

Option 1 : 45

**Given:**

The average of 13 natural numbers = 59

The average of the first 7natural numbers = 43

The average of the last 7 natural numbers = 73

**Formula Used:**

Sum of all numbers = Average of numbers × Number of terms

**Calculation:**

Sum of 13 natural numbers = 59 × 13

⇒ 767

Sum of the first 7 natural numbers = 43 × 7

⇒ 301

Sum of the last 7 natural numbers = 73 × 7

⇒ 511

The total sum of the first 7 and the last 7 natural numbers = 301 + 511

⇒ 812

The fifth number = Sum of the first 7 and the last 7 natural numbers - Sum of 13 natural numbers

⇒ 812 – 767

⇒ 45

**∴**** The seventh number is 45.**