Exam 4: Formulas and Problem Solving

Set up an equation and solve the following problem. Fawn invested a certain amount of money at 9% interest and $250 more than that amount at 11%. Her total yearly interest was $55.50. How much did she invest at 9% rate? $ __________

Solve the equation for the indicated variable. $6 x - 5 y = 13$ for $y$

18% of what number is 8.46?

Solve the equation. $\frac { h } { 6 } - \frac { h } { 7 } = 7$

A retailer has some earrings that cost him $6 each. He wants to sell them at a profit of 75% of the cost. What should be the selling price of the earrings?

Solve the equation. 0.3 x + 0.8(25 $-$ x ) = 0.5(25)

Solve the equation. $\frac { 9 } { 2 } w + \frac { 9 } { 2 } ( w + 8 ) = 36$

The cross products of a proportion are equal to each other.

Solve the equation for x . $\frac { x - 7 } { 35 } = \frac { y - 2 } { 10 }$

Set up an equation and solve the following problem. A tank contains 40 gallons of a 60% solution of anti-freeze. How much solution needs to be drained out and replaced with pure antifreeze to obtain a 90% solution? __________ gallons

Set up an equation and solve the following problem. Suppose that 20 gallons of a 20% salt solution is mixed with 20 gallons of a 30% salt solution. What is the percent of salt in the resulting solution? __________%

Selling price is the cost minus the profit.

Use the formula $i = P r t$ to reach a solution for the following problem. How much interest will be charged on a student loan if $8,820 is borrowed for 4 months at a 18% annual interest rate?

Solve the equation. $10 x + 11 \left( 1 \frac { 1 } { 2 } - x \right) = 93$

The expression for a value P to double itself is 2 P .

A retailer has some candle sets that cost her $25. If she sells them for $38.75, find her rate of profit based on the cost. $__________

Sally invested a certain sum of money at 6%, twice that sum at 7%, and three times that sum at 8%. Her total yearly interest from all three investments was $176. How much did she invest at each rate? Enter your answer as three numbers in the following order: the amount invested at 6%, the amount invested at 7%, the amount invested at 8%.

Solve the equation. 0.4 x + 0.9(10 $-$ x ) = 0.2(10)

11% of what number is 5.39?

How long will it take $1,000 to double itself if it is invested at 5% simple interest?