Work out 3.5 minus a quarter. Circle your answer. The options are three, 3.75, 3.25, or four.
Well, what we can do straight away is rule out two of the answers. And we can do that because we’ve got 3.5 minus a fraction. But it’s a positive fraction. So therefore, the result is gonna be less than 3.5. As 3.75 and four are both greater than 3.5, we can rule these out straight away. Okay. So now let’s get on and work out 3.5 minus quarter.
Well, first of all, we want to convert a quarter into a decimal. And it’s one of the common ones that we should know. We should know that a quarter is equal to 0.25. But if we’ve got this, we could work it out because one over four or one-quarter means one divided by four. So therefore, we could carry out this calculation using the bus stop method.
First of all, we’d see how many fours go into one, which is zero. And then, we’d have a decimal point. And then, we carry the one because we’d have a remainder of one. Then, we’d see how many fours go into 10, which is two, because two multiplied by four is eight. Then, there’s a remainder of two. So what we do is we carry this. And then, we see how many fours go into 20. And we can see that four goes into 20 five times. So we get our 0.25. Okay, great. We’ve got this. So now, let’s do the calculation.
So now, we have 3.5 minus 0.25. And we can work this out using column subtraction. So we have 3.5 minus 0.25. And what is worth doing at this point is adding a zero after the 3.5. And this is just because it helps us to line up our place values. And you must also make sure that the points or the decimal points are also lined up. Okay, great. So first of all, we’re gonna do zero minus five. Well, we can’t do this. So we have to borrow one from the next column up, which is the tenths column. So when we do that, we’re gonna have 10 minus five, which is just five.
Be careful here because a common mistake is that students see zero minus five and just get one and just do five minus zero, which would be five, which would give us the same value that we’ve got here in the hundredths column. However, we’d have one too many in the tenths column if we used that method. Then, we have four minus two, which is two. Then, finally, three minus zero, which is just three. So therefore, we’re left with 3.25. So that’s our third answer above. So we’ve circled that. And we can say that the correct answer to 3.5 minus a quarter is 3.25.
It’s worth saying that we could’ve found this by the process of elimination cause we could’ve also ruled out three. And we could’ve done that because we had 3.5 minus a quarter. Well, 0.5 or .5 is equal to a half. And a half minus a quarter is gonna be a positive result. So therefore, the answer must be greater than three. So that would’ve led us to the same answer, which is 3.25.