Mira has 20 gallons of water. She used 8 1/2 gallon to water the roses and 7 1/2 gallons to water lilies. How much water does she use have left?
20 - (8 1/2 + 7 1/2) = _________ gallons
how many half gallons?
started with 40 which is 2*20
first used 17 which is 2*8 +1
then used 15 which is 2*7 +1
so
40 - 17 - 15 = 8 half gallons
which is 4 whole gallons.
To find out how much water Mira has left, we need to subtract the amount of water she used from the total amount of water she started with.
Mira used 8 1/2 gallons of water to water the roses, and 7 1/2 gallons of water to water the lilies. So, the total amount of water she used is 8 1/2 + 7 1/2 = 16 gallons.
To find out how much water Mira has left, we need to subtract the amount of water she used (16 gallons) from the total amount of water she started with (20 gallons).
20 - 16 = 4
Therefore, Mira has 4 gallons of water left.