Class 2 and Class 1 * * *: 45× 2 = 90 people.

Class two has: 90-48=42 people.

Class three has: 42+3=45 people.

2.

The original sum of five numbers is: 10×5=50.

After changing one to 1, the sum of five numbers is: 5×9=45.

Decrease: 50-45=5

This number turned out to be: 1+5=6.

Dad is 27 years older than Xiaohong, and his age is four times that of Xiaohong. How old are Dad and Xiaohong after four years?

This year,

Xiaohong: 27(4- 1)= 9 years old.

Dad: 9×4=36 years old.

Four years later, dad and Xiaohong's age and:

9+36+4×2=53 years old

The product of the numbers a and b is 3698. If the number A is increased by 3, the product of the two multiplications is 3827. What was the initial number b?

B: (3827-3698)÷3=43

It takes 8 minutes to saw a piece of wood into 5 pieces and 8 pieces to divide seeds (14)? Have 20 minutes to saw into (1 1) segments?

Sawing into 5 segments requires 5- 1=4 times.

Each time: 8÷4=2 minutes.

It takes 8- 1=7 times to saw into 8 segments.

Need: 7×2= 14 minutes

20 minutes, 20÷2= 10 times.

It can be sawed as:10+1=11.

6 A class question and answer, 35 people answered the first question correctly, 33 people answered the second question correctly, 18 people answered both questions correctly, and there were (50) people in the class?

35+33- 18=50 people