Question

Geeta's average of four subject is 80.She needs on her fifth subject to raise her average to 84 is​

Answer 1

Answer: she needs score 100 in the fifth subject.

Explanation:

Let a subject is nₓ

Hence,

`\displaystyle\\(n_1+n_2+n_3+n_4)/(4) =80\\`

Multiply both parts of the equation by 4:

`n_1+n_2+n_3+n_4=(80)(4)\\n_1+n_2+n_3+n_4=320`

`\displaystyle\\(n_1+n_2+n_3+n_4+n_5)/(5)=84`

Multiply both parts of the equation by 5:

`n_1+n_2+n_3+n_4+n_5=(84)(5)\\(n_1+n_2+n_3+n_4)+n_5=420\\320+n_5=420\\320+n_5-320=420-320\\n_5=100`

Answer 2

a score of 100 is required

Explanation:

the average is calculated as

average =
`(sum)/(count)`

given her average for 4 subjects is 80 , then

`(sum)/(4)` = 80 ( multiply both sides by 4 to clear the fraction )

sum = 320

let x be the score required to raise average to 84 , then

`(320+x)/(5)` = 84 ( multiply both sides by 5 )

320 + x = 420 ( subtract 320 from both sides )

x = 100

she requires to score 100 in her fifth subject