1, 1 square meter = 100 square decimeter, so two fifths of the square meter =40 square decimeter, and half an hour is 0.5 hour, that is, 30 minutes, seven tenths of tons =700 kilograms, and three quarters of meters =75 centimeters.

2. There are two-sevenths fewer trees related to squirrels than cypress trees, and (cypress) trees × two-sevenths = (cypress trees are more than squirrels); This year's output is one eighth higher than last year's, and (last year's) output × one eighth = (this year is higher than last year's) output.

3. 80× 2/5 of1class is 32, and 80×1/4 of class 2 is 20.

4.24× 1/4 = 6 liters of milk, 6× 6/5 = 7.2 grams of calcium.