CPhill

Here's  a (i)   .....the other two are worked the same way

Average  = 80    ...so.....

[ 82 + 75 + 78 + 80 + ? ]  / 5  = 80     multiply by 5

82 + 75 + 78 + 80 + ?  = 400

315 + ?  = 400

?  =  400 -  315  =   85 is the % he needs

b   84 * 5  =  420........he only has 315...so...he needs  105 (%)  on the last test.....impossible

Diameter = 9in  = 3/4 ft    so.......the radius  = 3/8 ft

One rotation  = [ 2pi* r]  ft   =  2pi * (3/8) ft  =  3pi/4 ft

300 /   (3pi/4)  =    (4/3) * 300 /  pi  =   400 / pi   ≈ 127.32  = 127 rotations

The vertex is at  (h, k)  =  (0,4)

And  p = 8    ......so we have

y - k  = (1/ [4p] ) ( x - h)^2

y - 4  = ( 1 / [4 *8]) (x - 0)^2

y = (1 /32)x^2 + 4

-6x - 24y = -63

 6x -   4y = 14           add the equations  giving us

- 28x =  - 49        divide both sides by - 28

x = 49 / 28 =   7/2      sub this into either equation to find y

6(7/2) - 4y  = 14

21 - 4y  = 14

-4y  = 14 - 21

-4y  = - 7       divide by - 4

 y =  7/4

Just multiply the  number by .05  =  5 /100

Hard to see this, but I believe we have triangular pyramid wih a  base area of [14 * 18] / 2  =  126 cm^2 and a height  = 30cm

The volume = (1/3) base area * height  =   (1/3) (126cm^2) (30 cm)  = 1260 cm^3

We'd have to know something about the other acute angle.

Take their average

[4.5 + 6.7] / 2  =

11.2 / 2  =

5.6

Here's the Carrot :

And here's the  Caret   →   ^