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 180 seconds are required to make a 5-by-4 enlargement, find the time required for a 
enlargement.
A. 336 sec
B. 420 sec
C. 378 sec
D. 462 sec
Answer: C
Mathematics
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Solve the problem.The half-life of a certain radioactive substance is 13 years. Suppose that at time t = 0 , there are 20 g of the substance. Then after t years, the number of grams of the substance remaining will be N(t) = 20(1/2)t/26How many grams of the substance will remain after 39 years?
A. 0.88 g B. 1.77 g C. 7.07 g D. 3.54 g
Mathematics
Simplify by using the order of operations. Round your answer to the nearest hundredth, if necessary.49.6 - 5.4 ÷ 7.4 ? 20.3
A. 0.29 B. 121.25 C. 992.07 D. 34.79
Mathematics
Multiply. Write a mixed numeral for the answer.5
? 2
A. 14 B. 8 C. 10 D. 15
Mathematics
Write a fraction to represent the shaded area.
A. 1
or 
B. 1
or 
C. 2
or 
D. 2
or 
Mathematics