During a scuba dive, Lainey descended to a point 20 feet below the ocean surface. She continued her descent at a rate of 20 feet per minute. Write an inequality you could solve to find the number of minutes she can continue to descend if she does not want to reach a point more than 100 feet below the ocean surface.
Answer:
We know that she first descends 20 feet, and then she descends at a rate of 20 feet per minute. Basically, we have 20 feet which have to me summed with 20x, which expresses the ratio per minute, where x is minutes, and these terms cannot be more than 100 feet, so there are equal or less than 100 feet,
The expression would be:
\(20+20x\leq 100\)
If we solve this, we have
\(20+20x\leq 100\\20x\leq 100-20\\x\leq \frac{80}{20}\\ x\leq 4\)
Therefore, she cannot descent for more than 4 minutes.