Question

Pls answer Question 28 and 29 asap.

Answer 1

28. Answer:  86% decrease

Step-by-step explanation:

Original Sphere has a radius of 100%   →  r =1

Surface Area of Original Sphere:

S.A. = 4πr²

       = 4π(1)²

       = 4π

New Sphere has a diameter of 75%   →   d = 0.75    →    r = 0.375

Surface Area of New Sphere:

S.A. = 4πr²

       = 4π(0.375)²

       = 0.5625π

$\text{\% Change} =\dfrac{New - Original}{Original}\\\\.\qquad \qquad =\dfrac{0.5625\pi -4\pi}{4\pi}\\\\.\qquad \qquad =\dfrac{-3.4375\pi}{4\pi}\\\\.\qquad \qquad =-0.86$

The negative sign represents a decrease.

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29. Answer:  72 bottles

Step-by-step explanation:

Volume of a hemisphere is:

$V=\dfrac{2}{3}\pi r^3\\\\.\quad =\dfrac{2}{3}\pi (18)^3\\\\.\quad = 3888\pi$

Volume of a cylinder is:

$V=\pi r^2h\\\\.\quad =\pi (3)^2(6)\\\\.\quad =54\pi$

The number of cylinders needed is:

$\dfrac{3888\pi}{54\pi} = 72$