Ally and Jack buy some stickers. Ally buys a pack of 12 stickers for 10 pounds 49. Jack buys 12 single stickers for 99p each. How much more does Jack pay than Ally?
Sometimes when we’re out shopping, we can see the same thing in different shops for different prices. And this question is all about that sort of situation. Ally and Jack both buy 12 stickers. But they buy them in different ways and they pay different amounts. We’re told that Ally buys a pack of 12 stickers for 10 pounds 49. And we can see this illustrated in the picture.
The question then goes on to tell us that Jack buys his stickers on their own. He buys 12 single stickers and these cost 99 pence each. We know that this must be more expensive than Ally’s stickers because the final question asks us how much more does Jack pay. But at the moment, we don’t know how much Jack pays at all.
First, we need to calculate the total amount that Jack pays and then we need to use subtraction to find how much more he pays than Ally. So let’s start by calculating how much he pays. We know he buys 12 stickers and that they cost 99 pence each. So we need to work out the calculation 12 multiplied by 99. What do we know about the number 99 that would make this calculation easier?
We know that 99 is one less than 100. So 99 pence is 100 pence or a pound take away one pence. So we can use this fact to help us. 12 lots of 99 pence equals 12 lots of 100 pence take away 12 lots of one pence. We know that 100 pence is the same as one pound. So 12 multiplied by one pound equals 12 pounds. We know that 12 lots of one pence equals 12 pence.
And so, our subtraction becomes 12 take away 12 pence. What goes with 12 pence to make 100? 88. And so if we take away 12 pence from 12 pounds, we’re left with 11 pounds 88. This is the amount the Jack pays on all of his cards.
And if the question asks us how much does Jack pay, this would be the answer. But there’s more to it than that. The question actually asks us how much more does Jack pay than Ally. So we need to subtract to find the answer. 11 pounds 88 take away 10 pounds 49 will leave us with the difference.
Before we start, let’s include a decimal point within the equal signs at the bottom so that we don’t forget it. First, subtract the hundredths column. Remember these are hundredths because we’re talking about pounds here, hundredths of a pound or pennies.
We can’t subtract nine hundredths from eight hundredths. So we need to exchange one tenth for 10 hundredths. 18 hundredths take away nine hundredths leaves us with nine hundredths. That’s nine hundredths of a pound or nine pence. Seven tenths take away four tenths equals three tenths. That’s three tenths of a pound or 30 pence. One pound take away zero pounds leaves us with one pound. And we’ve got nothing left if we subtract one ten from one ten. And so, Jack pays one pound 39 more.
Another way we could have subtracted 10 pounds 49 from 11 pounds 88 was to do so mentally. 10 pounds 49 is very close to 10 pounds 50. So we could have started with 11 pounds 88 and taken away 10 pounds 50 to begin with.
First of all, take away 10 pounds. That would leave us with one pound 88. Then take away the 50 pence which takes us to one pound 38. And then adjust our answer by adding a penny because we’d subtracted 50 pence instead of 49 pence. One pound 38 plus one pence equals one pound 39.
So Jack and Ally both buy their stickers in different ways. They both end up with 12 stickers. But Jack pays one pound 39 more.