Solve the problem.A railroad tunnel is shaped like a semiellipse. The height of the tunnel at the center is 15 ft and the vertical clearance must be 
at a point 
from the center. Find an equation for the ellipse. 
A. 
+ 
= 1
B. 
+ 
= 1
C. 
+ 
= 1
D. 
+ 
= 1
Answer: D
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A 25-ft ladder leaning against a wall begins to slide. How fast is the top of the ladder sliding down the wall at the instant of time when the bottom of the ladder is 15 ft from the wall and sliding away from the wall at the rate of 6 ft/sec?
?
Hint: Refer to the accompanying figure. By the Pythagorean theorem, 
. Find 
when 
and 
.
?
?
a = 25; b = 6
?
What will be an ideal response?
Solve the problem.Strontium 90 decays at a constant rate of 2.44% per year. Therefore, the equation for the amount P of strontium 90 after t years is P = P0 e-0.0244t. How long will it take for 15 grams of strontium to decay to 5 grams? Round answer to 2 decimal places.
A. 4.50 years B. 450.25 years C. 45.03 years. D. 40.50 years
Find r if AB = 18 and AD = 30.
?
Fill in the blank(s) with the appropriate word(s).
Determine the most appropriate metric unit to go in the blank. Choose from L, ml, kg, g, and mg.The baby weighs 3.5 
.
A. mL
B.
| mg |
C. g
D.
| kg |
E.
| L |