# Thread: Algebra questions part 3

1. ## Algebra questions part 3

Need Help! Would like To know How to solve these..... Would like to know step by step(formula)

Numerical Skills/Prealgebra

10. If the total cost of x apples is b cents, what is a general formula for the cost, in cents,
of y apples?
A. b/xy
B. x/by
C. xy/b
D. by/x
E. bx/y

11. On a math test, 12 students earned an A. This number is exactly 25% of the total number of students in the class. How many students are in the class?
A. 15
B. 16
C. 21
D. 30
E. 48

12. This year, 75% of the graduating class of Harriet Tubman High School had taken at least 8 math courses. Of the remaining class members, 60% had taken 6 or 7 math courses. What percent of the graduating class had taken fewer than 6 math courses?
A. 0%
B. 10%
C. 15%
D. 30%
E. 45%

2. Question 10... The answer to this would be $\frac{b}{x}\times y$. Dividing the cost by the number of apples $x$ works out the cost per single apple. Then multiplying this value by $y$ gives the cost of $y$ apples.

For question 11, since 25% is a quarter of 100%, 12 students must be a quarter of the class. So to calculate the size of the class, simply do $12\times 4=48$.

Question 12... Okay, I'm not good at explaining things like this, and I'm not even sure my answer's right. All I did was $0.25 \times 0.6=0.15$ (this calculates the proportion of the graduating class that took 6 or 7 courses i.e. 15%), then I added this to the ones who did 8 or more maths courses, so 75% + 15% = 90%, meaning the remaining 10% must do fewer than 6 maths courses. So the answer's 10% I think.