When you add (i.e. never need to borrow), you can calculate the integer and fractional parts separately, and carry if necessary.
Integer part:
8+5-5=8
Fractional part:
9/10 + 3/4
find common denominator (=20)
18/20 + 15/20
=33/20
= 1 13/20
Carry the 1 to give
9 13/20
Can someone explain how to do this problem
8 9/10 + 5 3/4 - 5
2 answers
You need to express the whole thing in terms of a common denominator (the denominator is the bottom of a fraction). You've got two fractions in the calculation: (9/10) and (3/4), so the best common denominator is probably 20, because 9/10 = 18/20, and 3/4 = 15/20. Now, 8 + (9/10) = 89/10 = 178/20, and 5 + (3/4) - 5 is just (3/4) = 15/20 (because the two fives cancel out). So you've got 178/20 + 15/20, which is just 193/20. You can't simplify that fraction any more, so that's the answer. (If you actually work that fraction out you'll get 9.65.)
An alternative way to do it is to notice that both 9/10 and 3/4 are very easily expressed as decimals: 9/10 = 0.9, and 3/4 = 0.75. So you've actually got 8.9 + 5.75 - 5 = 8.9 + 0.75 = 9.65 as before. (But the form of the question suggests to me that you're supposed to do this by the first method, not the second.)
An alternative way to do it is to notice that both 9/10 and 3/4 are very easily expressed as decimals: 9/10 = 0.9, and 3/4 = 0.75. So you've actually got 8.9 + 5.75 - 5 = 8.9 + 0.75 = 9.65 as before. (But the form of the question suggests to me that you're supposed to do this by the first method, not the second.)