Answer:
Is this an exam? looks like it
Large sphere's radius = R,
small sphere's radius = r, R = 8r
surface area of a sphere (SA) = 4×pi×radius^2
So what we need is the SA of the larger in terms of the smaller sphere, so if:
SA (of R) = 4×pi×R^2, then plug in "8r" for "R"...
SA = 4×pi×(8r)^2 = 4×3.14×64r^2
SA = 12.57×64r^2 = 804 r^2
Therefore the SA of the larger sphere is 804 times the SA of the smaller sphere.
I hope that makes sense!
Answer:
The missing number is 4
Step-by-step explanation:
Given
21 x 39 x _____ x 19 divided by 12 = 5187
Required
Fill in the gap
Let the missing number be represented with y; So, the expression becomes

Multiply both sides by 12


Rearrange the expression on the left hand side


Divide both sides by 15561



Hence, the missing number is 4