Question 1160234
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A "simplified" way of answering the question for a 9-year-old is whatever "works" for the 9-year-old.<br>
We can only guess what might work well.  Certainly we don't want to use formal algebra....<br>
Here are my thoughts for explaining this to a 9-year-old.<br>
The problem is well presented for solving by a 9-year-old, in that the first question asked is key to one method for making solving the problem relatively easy.<br>
Each raisin bar costs 12p "extra"; so the "extra" cost for the 9 raisin bars is 9*12p = £1.08.<br>
ANSWER to the first question: 9 raisin bars cost £1.08 more than 9 nut bars.<br>
We're done with the first question.  Now we use that result to solve the rest of the problem.<br>
Having accounted for the "extra" cost of the raisin bars, we have left 9+12=21 cereal bars, each costing the same amount; and the amount remaining is £5.28=£1.08 = £4.20.  So the cost of each nut bar is £4.20/21 = 20p.<br>
So each nut bar costs 20p, and each raisin bar costs 20p+12p = 32p.<br>
ANSWER to second question: A raisin bar costs 32p.<br>