91Ó°ÊÓ

The formula \(E=I R,\) called Ohm's law, is used in electronics. Solve for \(I\), and then calculate the current \(I\) if the voltage \(E\) is 48 volts and the resistance \(R\) is 12 ohms. Current has units of amperes.

Use the subtraction property of equality to solve each equation. Check all solutions. $$a+9=-12$$

Solve each inequality and graph the solution on the number line. $$-4 < \frac{x-2}{2} < 6$$

Express each solution as an inequality. A student has test scores of \(68,75,\) and 79 points. What must she score on the fourth exam to have an average score of at least 80 points?

The energy of an atomic bomb comes from the conversion of matter into energy, according to Einstein's formula \(E=m c^{2} .\) The constant \(c\) is the speed of light, about 300,000 meters per second. Find the energy in a mass \(m\) of 1 kilogram. Energy has units of joules.

The perimeter of an equilateral triangle is at most 57 feet. What could be the length of a side? (Hint: All three sides of an equilateral triangle are equal.)

Use the division property of equality to solve each equation. Check all solutions. $$25 x=625$$

Auto repairs A mechanic charged \(\$ 20\) an hour to repair the water pump on a car, plus \(\$ 95\) for parts. If the total bill was \(\$ 155\), how many hours did the repair take?

Water billing The city's water department charges \(\$ 7\) per month, plus 42¢ , for every 100 gallons of water used. Last month, one homeowner used 1,900 gallons and received a bill for \(\$ 17.98 .\) Was the billing correct?

Clearance sales Sweaters already on sale for \(20 \%\) off the regular price cost \(\$ 36\) when purchased with a promotional coupon that allows an additional \(10 \%\) discount. Find the original price. (Hint: When you save \(20 \%\), you are paying \(80 \%\) )