Inji goes to a charity shop and buys one CD costing three pounds 70, one toy costing 89 pence, two identical vases. Inji pays with a 10 pound note and receives 41 pence change. Calculate the total cost of one of the vases.
The first thing we need to do is actually work out the total cost of all the things that Inji goes and buys from the charity shop. And the way we’re going to work that out is by doing 10 pounds minus 41 pence. And that’s because Inji paid with a 10 pound note and received 41 pence change.
There are actually a number of ways we can work out this calculation. One way I’m going to show you is to actually convert the pounds into pence so that we’re dealing completely in pence. So we’ve got 10 pounds. This is equal to 1000 pence then minus 41 pence. And we know that 10 pounds is equal to 1000 pence because actually what we’re gonna do is multiply 10 by 100 which gives us 1000. And that’s because we know that one pound is equal to 100 pence.
So now, if we look at the column subtraction. We’ve got zero minus one which we can’t do. And we can’t borrow from the tens or the hundreds. So we have to borrow from the thousands. And now, we’ve actually got 10 in the hundreds column. But what we need to do now again is borrow from this to increase our tens. So now we have 10 in the tens column.
And now so that we can actually do the first part of the calculation which is in the units column, what we need to do actually is actually take away and borrow from the ten. So then finally in the units column of our pence, we have 10 minus one which is nine. Then moving along, we have nine minus four which is five. Then, we have nine then minus zero, which means that we’ve got nine. So that leaves us with 959 pence.
And what we can do with this is actually divide it by 100 to turn it back into pounds. And when we do this, we’re gonna get nine pounds and 59 pence.
So now, another method we could have used if we’re confident with our money calculations would be to actually have our 10 pounds then subtract 40 pence which give us nine pounds 60 then subtract one more pence would give us out nine pounds 59 and that’s because what we wanted to do is actually subtract 41 pence as this was the change left over after Inji had paid.
So now, the next stage in the question is to actually work out the cost of two vases because eventually we want to find the cost of one vase, but we need to find out the cost of two vases first.
And the way we’re gonna work this out is by having nine pound 59 which is the total minus three pound 70 cause that was the cost of a CD then minus 0.89 pounds or 89 pence because that was the cost of the toy. And you can see here that I’ve actually converted it into pounds from 89 pence, just another way of writing it which will give us five pounds.
So the cost of two vases is five pounds because actually that’s the total amount minus the cost of the CD and the toy. The way we could have found five pounds is obviously using the mental method. But also, if we want to use a written method, what we do is first of all subtract three pounds 70 from nine pound 59. And what I’ve done here is actually convert them both into pence to make life easier.
So we’ve got 959 minus 370. So first of all, we have nine minus zero, which is just nine. And then, we’ve got five minus seven which we can’t do. So then, we borrow from the place value above, so the hundreds. So then, we’ve got 15 minus seven which is eight. And then, finally, we’ve got eight minus three which is five. So we got 589 pence or five pound 89.
So then, what we need to do is actually subtract the cost of the toy. So when we do that, we’ve got 589 minus 89. Well, nine minus nine is zero, then eight minus eight is zero, and we’ve just got our five. So we get an answer of 500 or five pounds.
Okay, great, so now, we got the cost of two vases. But we haven’t finished yet because what we need to do is actually find the cost of one of the vases. So therefore, to find the cost of one vase, what we’re gonna do is divide five pounds by two. So what we can do is actually use the bus stop method to do this.
So to do twos into five, well they go twice remainder one, remembering to put our decimal point cause we’re dealing with pounds here. Then, twos into 10 go five times with no remainder. And then, finally, twos into zero don’t go. So therefore, we can say that the cost of one of the vases is going to be two pounds and 50 pence.