Question

Avareage age of 7 family members is 75 years. But avarage age of 6 of them is 74 years 6 months. What is the age of 7th family member.?​

Answer 1

Answer:

78 years

Step-by-step explanation:

Total Age of 7 family members = 75 × 7 = 525 yrs = 525 × 12 = 6300 months

Total Age of 6 of them =( 74 yrs 6 months)× 6 = 447 yrs = 5364 months

--> 6300-5364 = 936 months = 78 yrs

Answer 2

The age of the 7th family member is 78 years.

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Let's understand a few concepts:

To solve the above problem we will use the following formula of average:

$\boxed{\bold{Average = \frac{Sum \:of\:observations}{No.\:of \:observations} }}$

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Let's solve the given problem:

The average age of 7 family members = 75 years

The no. of family members = 7

∴ The sum of ages of 7 family members = 75 × 7 = 525 years

The average age of 6 family members are,

= 74 years 6 months

= 74 years + $\frac{6}{12} \:years$ . . . [ ∵ 1 month = $\frac{1}{12}$ calender year ]

= 74 years + 0.5 years

= 74.5 years

The no. of family members = 6

∴ The sum of ages of 6 of the family members = 74.5 × 6 = 447 years

Now,

The age of the 7th family member will be,

= [Sum of ages of 7 members] - [Sum of ages of 6 members]

= 525 years - 447 years

= 78 years

Thus, the age of the 7th family member is 78 years.

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