Question

Mrs Lim bought a number of plates at an average price of $6. She decided to buy another plate which cost $18. The average price of all the plates then became $8. What was the total number of plates Mrs Lim bought in all?​

Answer 1

Answer: 6

Explanation:

Let x represent the number of plates bought for $6

Let y represent the Total number of plates bought = x + 1

Remember that Mrs. Lim bought another plate for $18

Total cost ÷ Total plates = Average Cost

`(6x+18)/(x+1)=8\\`

6x + 18 = 8(x + 1)

6x + 18 = 8x + 8

18 = 2x + 8

10 = 2x

5 = x

y = x + 1

= 5 + 1

= 6