Answer:
8. $35.10
9. $59.63
10. $13.43
11. $70
12. Take the percent you pay (100-the discount) as a decimal and multiply it by the regular price.
Step-by-step explanation:
For finding the price we pay during a sale, we focus on the percent we pay. If 22% off is the sale, then we spend 78% or 100-22-78. We use this percent byb multiplying the price with a decimal. We convert percents into decimals by dividing the percent number by 100. For example, 78% divided by 100 becomes 0.78.
8. Percent off is 22%. We pay 78%=0.78.
45(0.78)=$35.10
9. Percent off is 33%. We pay 67%=0.67.
89(0.67)=$59.63
10. Percent off is 44%. We pay 56%=0.56.
23.99(0.56)=$13.43
11. Percent off is 75%. We pay 25%=0.25.
279.99(0.25)=$70
12. See explanation above.
I find it convenient to look at the differences and the rate at which those differences are made up.
8. Jim is closing the $150 gap at the rate of $7.50 per week. He will catch up in
... 150/(7.5/week) = 20 weeks
9. At noon, the price of Stock A has increased by 0.05×3 = 0.15, so is now $15.90, which is $0.63 more than Stock B at that time. The prices are closing the gap at the rate of $0.05 +0.13 = $0.18 per hour, so will be the same after
... $0.63/($0.18/hour) = 3.5 hours . . . . after noon, at 3:30 pm
_____
You can also write and solve equations for the prices of the stocks. Or you can use a graphing calculator to tell you the solution. When equations are involved, I like to solve them the simplest possible way: let technology do it.
You are given the value at a time, and the rate of change of that value, so the equations are easily written in point-slope form. You will note that the common price at 3:30 pm (15.5 hours after midnight) is one that is not a whole number of cents. (That's usually OK for when trading stocks.)
The First 10 multiples of 4 is:
4
8
12
16
20
24
28
32
36
40