2, (1/9) or (3/7)

3. (15-9) ÷ 15=3/5 A: 3/5 of this pair of cement was used.

50 ÷(50+400)= 1/9 A: sugar accounts for 1/9 of sugar water.

The number that can be divisible by 12 and 16 at least twice is between 30 and 50, and only 48 answers: there are 48 students in this class.

A: 5÷2=2.5 (hours) =2 hours and 30 minutes, B: 8÷3=8/3 (hours) =2 hours and 40 minutes. A it's done quickly.

6× 8 = 48 () A: The side length of this square is at least 48㎝.

5, assuming that it can't be weighed at once, put four scales 1 time on the left and right sides, then put two scales 1 time on the four sides of the heavy side, and then put two scales 1 time on the two sides of the heavy side, so the total number of * * * is three times.

The same reason as the above question: 4 times.

6. The mother-child difference is 56-30= 16 (years old). Suppose the age of the son is x and the mother is x+ 16, and the equation is:

x+(x+ 16)=46

x= 15

A: Son 15 years old, mother 3 1 year old.

I finished it with a little effort, and now primary school mathematics is so difficult! I hope it helps you!

I can understand your pains as a parent!