Question

Here are five number cards.

2
5
7
8
9
One of the cards is removed and the mean average
of the remaining four number cards is 6
Which card was removed?
You must show your working.
Note: Please make sure your final answer says card ...

Answer 1

If the mean of the four remaining cards have an average of 6, then the sum of the cards should be 24 (Average of 6 times 4 cards = 24)

This means that if you add up all 5 cards, and subtract 24 from the sum of all 5, you should get the one that was removed

2+5+7+8+9=31

31-24= 7

This means card 7 is the one that was removed

Answer 2

card 7

Explanation:

since the mean of the four remaining cards is 6, then the four cards must add up to 24 since 24/4=6. Currently, the five cards adds up to 31, so 7 should be removed to bring the sum of the four remaining cards to 24.