Solve the problem.The time T necessary to make an enlargement of a photo negative varies directly as the area A of the enlargement. If 72 seconds are required to make a 3-by-4 in. enlargement, find the time required for a 4-by-7 in. enlargement.
A. 140 seconds
B. 196 seconds
C. 168 seconds
D. 224 seconds
Answer: C
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Find the area of the shaded part of the figure if a = 6, b = 9, c = 2.
?
?
A. 45 B. 26 C. 120 D. 66 E. none of these
Solve the problem.A bacterial culture has an initial population of 10,000. If its population declines to 4000 in 4 hours, when will its population be 2530? Assume that the population decreases according to the exponential model.
A. after 5 hr B. after 7 hr C. after 9 hr D. after 6 hr
Find the surface area of the circular solid. Unless otherwise specified, use 3.14 for ? and round your answer to the nearest tenth.A sphere with r = 
in
A. 1.8 in2 B. 2.2 in2 C. 8.7 in2 D. 2.9 in2
Solve the problem.The pitch P of a musical tone varies inversely as its wavelength W. One tone has a pitch of 254 vibrations per second and a wavelength of 19.2 ft. Find the wavelength of another tone that has a pitch of 358 vibrations per second. Round to the nearest tenth.
A. 0.1 ft B. 0 ft C. 13.6 ft D. 4736 ft