General Math Questions?

Question

1. Find the volume of a sphere whose radius is 3cm. Use 3.14 for \Delta.

A. 37.68cm
B. 84.78cm
C.113.04cm
D. 904.32cm

2. What percent of 45 is 18

A. 45%
B. 40%
C. 25%
D. 18%

3. Subtract 7.8-(-5.3)

A. -5.3
B. 2.5
C. 12.1
D. 13.1

4. It takes 3/4 cup of brown sugar to make one batch of chocolate chip cookies. How much is required for 6 batches.

A. 12 cups
B. 8 cups
C. 4 1/2 cups
D. 3 cups

5. Subtract and simplify 3/10 - 5/15

A. 9/4
B. 1/5
C. 1/6
D. 1/25

Please use just a brief comment and the answer.

Answer 1

1) volume is (3.14)(3)^3 = 84.78
( ans : B)
2) 45 : 18
100 : x

x= 100* 18/45
x= 40 % ( ans : B)
3) 7.8 + 5.3 = 13.1 ( ans : D)
4) 3/4 * 6 = 4.5 ( ans : C)
5) 3/10 -5/15 = 3*3/30 - 5*2/30 = -1/30 Ans not in the list

Answer 2

I got the same answers as above but on #5 i got 1/5

3/10-5/15=x simplifies into 3/10 - 1/3 = x

so when you have 3 portions(tenths) and take away one third of those 3 portions, youre left with 2 portions(tenths) so the answer is 2/10 which simplifies down to 1/5.

Answer 3

1. C
2. B
3. D
4. C
5. i don't think the answer is there.

If you want to know how i did them:

1. The formula for a spheres volume is:
4/3(pie)r^3
now plug in the radius given, which is 3 and you get:
4/3(pie)3^3
plug that all in to your calculator and you get answer C.

2. you have to set up a proportion.
but i'm to lazy and i used http://www.marshu.com/articles/calculate-percent-with-simple-number-percentage-calculator.php

3. 7.8-(-5.3)
when you see to negatives next to each other like that you turn them into an addition sign:
7.8+5.3
now add them and you get:
answer D.

4. you just do 3/4 times 6 and you get 4.5 which could also be shown as 4and 1/2. answer C.

5. i dont think the answer is there because the answer should be negitave.

Answer 4

The answer to # 5 should be -1/10, which is not included in your list.

3/10 = 9/30
5/15 = 10/30
9/30 - 10/30 = -1/30