Unformatted text preview: ‘?3. $700 was invested at 6% compounded monthly. How much money will be in the account aﬁer 1.5
years? 72. How much money should be invested {10W at 8% compounded continuously to get $2500 after 5
years? 73. How long does it take for an investment to double in value if it is invested at 8% per annum
compounded monthly? Compounded continuously? 74. The halflife of radium is 2590 years. If lOgrams is present now, how much will be present in 50
years? 75. A culture ofbacieria obeys the law of nainhibited growth (N6) = N0 ekt ). If 500 bacizeria are
present initially and there are 800 after one hour, how many will be present in the culture after 5 hours?
How long is it until there are 20,000 bacteria? Chapter 12 76. Solve the following system of equations. If there are no solutions, say so. If there are inﬁnitely
many solutions, describe the solution set. )r5x~y=i3
a
2x+3y212
b.) "2x+y=1
‘l4x+2y:3
) x+2yz4
c
{231:8—43!
V 2x~y=m1
<3) 2 .2»
2x +y «—1
. =4
e) I?) 12372 wxy + y2 = 8
7?. Four large oheeseburgers and two chocolate shakes cost a total of $7.90. Two shakes cost 15
¢ more than one cheeseburger. What is the cost of cheesoburger? A shake?
78. Graph ﬁle inequality
21) 2x + y > 6
b} y > X2 —l
79. Graph ihe system of inequalities
2x + y S 4 w
x + 5}; 2 5
.3: 2 0 l
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