Common denominators!
If you have to add... 3 fractions with 4 as the denominators:
Then you can combine the numerators:
a/c+ b/c = (a+b)/c and a/d + b/d + c/d = (a+b+c)/d
Let's plug in the numbers.
a=3, b=1, c=1, d =4
3/4 + 1/4 + 1/4 = 5/4 or 1 1/4!
So the equation for the problem:
Lt = L1+ L2 + L3 + L4 or
L4 = Lt - L1 - L2 - L3 Plug in the numbers
L4 ( remains ) = L total, 72 - L1 ( first cut at 30 3/4 ) - L2 ( second cut 12 1/4 ) - L3 ( 16 1/4 )
So 72 - 30 - 12 - 16 - 3/4 - 1/4 - 1/4 =?
( break this down into simple terms and do it in your head...
72 - 30 = 42, 42 - 21 = 30, 30 - 16 = 14, 14 - 3/4 = 13 1/4 - 1//4 = 13 - 1/4 = 12 3/4!
