A divided by B equals a:b(a to B), so a:b(a to b)=2.5.

2. Answer 15:8

The ratio of number A to number B is 3:2, and the ratio of number B to number C is 5:4. You can multiply the number A and the number B by 60 (3 * 5 * 4 = 60) respectively to get that the number A is 180 and the number B is 120. Divide the number b by 5, multiply the number c by 4 to get the number c is 96, and the ratio of the number a to the number c is 65438+.

3. Answer 3.6 * 3÷ (1+2+3) *1=1.8.

If the average value of three numbers is 3.6, the sum of three numbers is 10.8(3.6*3), and the ratio of three numbers is 1:2:3. Divide 10.8 into six parts (1+2+3), and the smallest number is 1.8.

4. Answer 9÷(8-5)*(5+8)=39 people.

The ratio of the number of people in the art group to the number of people in the art group is 5:8, which can be understood as two groups * *13, the art group accounts for 5, the art group accounts for 8, and the number of people in the art group is 9 more than that in the art group, so it can be concluded that each group is 3 [9/(8-5), and the total number of people in the two groups is 3* 13.

5. Answer 30 ÷ (1-1/4-1/4) = 60 kg.

Pour a quarter of the water in barrel B into barrel A, and the water in barrel A is equal in weight, so the water in barrel A is half of that in barrel B (barrel B needs a quarter of the water to be balanced with the water poured into barrel A), and the water in barrel B is 60kg.