Question

The radius of a sphere is doubled . By what factor does the surface area of the sphere change ?

A. 1/4
B. 1/2
C. 2
D. 4

Answer 1

@jazy

Answer 2

might want to write the formula for surface area

Answer 3

Area i believe has r^2 in it; so (2r)^2 pops out a 2^2 factor

Answer 4

\[A=4\pi r^2\]

Answer 5

Okay . Im still lost .

Answer 6

how do I know the ratio of the volume ?

Answer 7

Sorry I meant: The ratio of the Area = ratio of sides, squared.

You know that the measures are doubled. So 1:2 is the original ratio. Now square it.

\[\large 1^2 : 2^2\]

Answer 8

2:4

Answer 9

No, 1^2 = 1 * 1 = ?

Answer 10

1

Answer 11

Right, so whats the ratio?

Answer 12

1/4

Answer 13

Perfect!

Answer 14

The slant heights of two simlilar pyramids are in the ratio 1:5 . The volume of the smaller pyramid is 60 m ^3 . What is the volume in cube meters of the larger pyramid ?

Answer 15

@Noemi95

Answer 16

The ratio of 1:5 means that for every one large pyramid, 5 small pyramids make up the length of a dimension. So in this case, the height, width and depth of the larger pyramid are all 5 times longer than the small pyramid.

So we can multiply the change in dimensions together to work out how much the volume has changed. 5 * 5 * 5 = 125.
Here we see the volume of the large pyramid is 125 times larger than the smaller one.
The volume of the smaller pyramid is 60, so:
60 * 125 = 7500.

Answer 17

Thank you so much .

Answer 18

No problem Lexi!(: