Question

Trevor needs a 93 on his second quiz to have a quiz average of 90. What score did Trevor receive on his first quiz?

Answer 1

87

Explanation:

The average of his score can be given by: `(93+"his first quiz mark")/2=90`

`93+"his first quiz mark"=90times2`

`93+"his first quiz mark"=180`

`"his first quiz mark"=180-93=87`

Answer 2

To find the average... we always have to add all the numbers and divide it by the number of the numbers

For example....

Find the average of `5,9,123`

Add 'em up

`137`

Three number added this up... so divide this number by 3 to find average

`137/3=45.bar666`

Here... `45.bar666` is the average of the three numbers

Back to the question

Let... the first quiz points be `x`

Then total would be `93+x`

Two numbers would give the average `90` so....

`(93+x)/2=90`

`93+x=180`

`color(blue)(x=87`