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Bunny27

P6 Mathematics

Question post on Sun, 20/09/2020 5:57pm

Hi,

Can someone help to explain this qns?

Thanks

Answer

BigDevil · Answer 1 · Post on Sun, 20/09/2020 6:14pm

Average price of 14 books -> u

Total price of 14 books -> 14u

Average price of 12 books -> u + $2.55

Total price of 12 books -> 12(u + 2.55) = 12u + 30.6

14u = (12u + 30.6) + (26.50 × 2)

2u = 83.6

u = 41.8

Average of books after adding 2 books at $26.50 each -> $41.80

Bunny27 · Answer 2 · Post on Sun, 20/09/2020 6:20pm

Bunny27 Post on Sun, 20/09/2020 6:20pm

Thank you 😊

BigDevil · Answer 3 · Post on Mon, 21/09/2020 12:11am

While the problem can be solved by formulating equations as I had done in the first solution, I think it would be good for the child to understand the concept of averages.

When the average decreased by $2.55 after adding 2 new books, the 12 original books “lost” $2.55 in value.

These amounts were “added” to the prices of the 2 new books, so that their prices appeared to be same as the other 12.

So, the new average is simply $26.50 + (6 × $2.55) = $41.80

BigDevil · Answer 4 · Post on Mon, 21/09/2020 12:11am

While the problem can be solved by formulating equations as I had done in the first solution, I think it would be good for the child to understand the concept of averages.

When the average decreased by $2.55 after adding 2 new books, the 12 original books “lost” $2.55 in value.

These amounts were “added” to the prices of the 2 new books, so that their prices appeared to be same as the other 12.

So, the new average is simply $26.50 + (6 × $2.55) = $41.80