Question

Sum of 5 numbers is 240. Average of first two numbers is 30 and that of last two numbers is 70. What is the third number (middle number)?​

Answer 1

Answer:

The third number is 40.

Step-by-step explanation:

Given :

• Sum of 5 numbers is 240.

• Average of first two numbers is 30 and that of last two numbers is 70.

To find :

the third number

Solution :

Let the five numbers be a, b, c, d and e.

We know,

$\longrightarrow \rm Average=\dfrac{sum \ of \ observations }{number \ of \ observations}$

Average of first two numbers = 30

 $\sf \dfrac{a+b}{2}=30 \\\\ \implies a+b=30 \times 2 \\\\ \implies a+b=60$

Average of last two numbers = 70

$\sf \dfrac{d+e}{2}=70 \\\\ \implies d+e=70 \times 2 \\\\ \implies d+e=140$

The sum of five numbers = 240

⇒ a + b + c + d + e = 240

⇒ 60 + c + 140 = 240

⇒ c + 200 = 240

⇒ c = 240 - 200

⇒ c = 40

∴ The third number is 40.