Answer:
10/12 can be approximated by 1
3/8 can be approximated by 1/2
so the answer to the subtraction must be really close to 1-1/2 = 1/2 = 0.5
Step-by-step explanation:
The real solution can be found by converting to numerator 24, which is the LCM, or Lowest Common Multiple of numerators 12 and 8.
10/12 = 20/24
3/8 = 9/24
Now the subtraction is (20-9)/24 = 11/24 ≈ 0.4583
So the actual result 0.4583 is actually pretty close to 0.5.
A benchmark value is nothing more than a really simple fraction or integer (1/2, 1/3, 1, 2, ...) that you know where to plot on the number line.
Making approximations can serve as a double check to see if you didn't make any mistakes on the actual calculation.
