If he drank 80% of his water on his entire hike, how much did he drink?

The purpose of this warm-up is to elicit the idea that tape diagrams can be used to think about fractions of a whole as percentages of the whole, which will be useful when students interpret and draw tape diagrams in a later activity. While students may notice and wonder many things about these images, the important discussion points are that there are two rectangles of the same length, one of the rectangles is divided into four pieces of equal length, and a percentage is indicated. 80 percent of what number is 100?
100 is 80% of 125

Steps to solve "100 is 80 percent of what number?"

We have, 80% × x = 100
or,
80
100
× x = 100
Multiplying both sides by 100 and dividing both sides by 80,
we have x = 100 ×
100
80
x = 125
If you are using a calculator, simply enter 100×100÷80, which will give you the answer.

How many groups are there?