Say What the Number Means

You'll learnto get the units from the integrand and the variable, to build an amount from a starting amount plus a change, to keep four different questions about one tank apart, and to write the sentence that earns the interpretation point.

Water runs into a tank and out of it at the same time. One setup produces four correct numbers, and three of them are the wrong answer to whichever question you were actually asked. Twelve short steps; press Next for each one.

12 STEPS · 6 QUICK CHECKS · A RATE IS A HEIGHT, AN AMOUNT IS AN AREA · v2

A rate is a height at one instant; an amount is an area across an interval

Before you start

What you're looking at

One tank, for the whole animation. Water enters at one rate and leaves at another, both in gallons per minute, and 50 gallons are already there when the clock starts.

The question

Which of four things is being asked for: a rate at one instant, how much came in, by how much the amount changed, or how much is there now?

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