Daughter is in 5th grade and I have no idea how to solve this math problem!
5 3/4 – 6 3/4
Obv you cannot subtract 5 from 6. You also can’t borrow the 3 from the 5 and make it a new mixed number. What do you borrow from? I’ve googled and seriously cannot figure this out.
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Former teacher and homeschool math support here: if you’re working this out on your own, go with the easiest method (fractions cancel out, 5-6 = -1). But homework is usually about practicing a particular skill. The whole point of the lesson might be to gain proficiency in converting mixed numbers to improper fractions and back again. As I have said many times over the years, “Please read the instructions thoroughly.”
I think it makes sense to look at this problem generally.
A (B/C) is also the same thing as ((AB)/C). For a problem like ((AB)/C) plus or minus ((DE)/F), we can’t really do anything with this. We want the same denominator (we want C and F to be the same thing). We can do this by realizing that ((AB)/C) is the same thing as ((2AB)/(2C)).
((FAB)/(FC)) plus or minus ((CDE)/(CF)) makes it so that the denominator is the same on both sides (CF or FC), and then you can add or subtract FAB with CDE. Afterwards, we can divide the top result by your denominator.
To use your numbers:
5 (3/4) – 6 (3/4)
15/4 – 18-4
-3/4.
Let’s say we instead had
5(3/4) – 6(3/5)
(15/4) – (18/5)
((5×15)/(5×4)) – ((4×15)/4×5))
(75/20) – (72/20)
3/20.
You have to simplify the problem to common terms or denominators (although its kind of already simplified).
So 5 3/4 becomes 23/4
And 6 3/4 becomes 27/4
23/4 – 27/4 is already in common terms so were good here.
The Answer becomes -4/4 which equals -1.
Bob has 23 slices of pizza (each pie has a 4 slices; he has 5 3/4 pies left). Joe is so hungry he orders 27 slices. How many more slices does Bob need to feed Joe? 4. 1 whole pie.
The core problem that you are going to have here is that there’s 10 ways to solve this problem, but your daughter has likely only been taught one of those ways.
For me, how I would do it is to turn these mixed (whole number and a fraction) numbers into just fractions. So 5 and three quarters turns into 23/4 and 6 and three quarters turns into 27/4.
Next step would be to use cross multiplication to make a common denominator but that’s already the case here (the bottom part of the fraction is already the same.
So we have 23/4 – 27/4. When subtracting fractions with a common denominator you just substract the top part and leave the denominator the same in the result. SO 23-27= -4 so the overall answer is -4/4 and we can reduce that to -1.
That’s how I would solve the problem, but it’s been a LOOOOONG time since i was in 5th grade and they might be teaching newer methods now. It’s not that the answer would be different, it’s how you get there that might be different.
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