A scuba diver descends at a rate of \(-1.5\) meters per second. How long does it take to reach a depth of \(-18\) meters from the surface?
- \(9\) seconds
- \(12\) seconds
- \(16.5\) seconds
- \(27\) seconds
Students will build Grade 7 mastery of rational number operations in extended contexts using models, equations, and test-style reasoning.
A scuba diver descends at a rate of \(-1.5\) meters per second. How long does it take to reach a depth of \(-18\) meters from the surface?
An ocean temperature is changing at a rate of -0.3°C per hour. If the current temperature is 12°C, what will the temperature be after 5 hours?
Maria's bank account has a balance of \($85.50\). She withdraws \($12.75\) twice in one week. What is her new balance?
A football team gains 15 yards on first down, loses 4 yards on second down, then gains 8 yards on third down. What is the net yardage change for this series?
A hiker is at an elevation of \(1,450\) feet. She climbs up \(325\) feet, then descends \(180\) feet. What is her final elevation?
A swimmer completes laps in \(\frac{3}{4}\) minute during the first 9 minutes. Then her pace slows and she takes \(\frac{7}{8}\) minute per lap for the next 7 minutes. How many total laps does she complete?
A recipe calls for \(\frac{2}{3}\) cup of sugar and \(\frac{3}{4}\) cup of flour. If you make 2 batches, then use \(\frac{1}{2}\) of that total sugar for a second dessert, how much sugar remains?
A temperature reading shows -5°F in the morning. By afternoon, the temperature increases by 18°F. What is the afternoon temperature?
Time \(=\) distance \(\div\) rate. The diver descends \(18\) meters at \(1.5\) m/s: \(18\div1.5=12\) seconds.
Temperature change \(= -0.3 \times 5 = -1.5°\)C. New temperature \(= 12 + (-1.5) = 10.5°\)C.
Two withdrawals: \(-$12.75 - $12.75 = -$25.50\). New balance: \($85.50 - $25.50 = $59.00\).
Net change \(= 15 - 4 + 8 = 19\) yards.
Final elevation \(= 1,450 + 325 - 180 = 1,595\) feet.
First 9 minutes: \(9 \div \frac{3}{4} = 12\) laps. Next 7 minutes: \(7 \div \frac{7}{8} = 8\) laps. Total: \(12 + 8 = 20\) laps.
Total sugar for 2 batches \(= 2 \times \frac{2}{3} = \frac{4}{3}\) cups. Sugar used for second dessert \(= \frac{1}{2} \times \frac{4}{3} = \frac{2}{3}\) cups. Remaining \(= \frac{4}{3} - \frac{2}{3} = \frac{2}{3}\) cups.
Afternoon temperature \(= -5 + 18 = 13°\)F.