What is the volume of the right prism?
900cm3
1251cm3
1440cm3
1042.5cm3

The formula for volume of a trapzoidal prism is V=(L)*(H)*(A+B)/2. So, multiply 10 times 12 to get 120cm. Add together 3 and 12 and then divide by 2 to get 7.5. Multiply 7.5 and 120 to get 900cm.

Answer=900cm cubed

12 Birds

To solve this problem, work it from the end towards the beginning.

Number of birds left = 4

Three more birds flew into the branches of a nearby tree. So you lost 3 birds. Add them to the total giving you 7.

Two birds left the bird feeder to go to another stationed a few feet away. So you had a loss of 2 birds. Add them to the total giving you 9.

On fourth of the birds flew away when they were startled by a noise. Now we have something. We know that after one fourth flew away, 9 were left.

X - (1/4)X = 9

Merge the X terms.

(3/4)X = 9

Divide both sides by 3/4

X = 9/(3/4)

X = 9/1 * 4/3

X = 36/3

X = 12

So the number of birds at the feeder initially was 12.

To prove it.

Start with 12. One fourth flew away, leaving 9.

Two more leave, leaving 7.

Three more leave, leaving 4.