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Robbie read 229 pages of a storybook over 3 days. On Day 1, he read some pages. On Day 2, he read 90 pages more than he did on Day 1. On Day 3, he read 10% less pages than on Day 2. How many pages did Robbie read on Day 1?

Aug 9, 2023

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Let p represent the number of pages Robbie read on Day 1.

Since we do not yet know how many pages Robbie read on Day 1, I will represent that as the following:

Day 1: $$p$$ pages

Since Robbie read 90 more pages than Day 1, that can be represented mathematically as follows:

Day 2: $$p + 90$$ pages

If Robbie read 10% fewer pages than on Day 2, then Robbie effectively read 90% of the number of pages on Day 2.

Day 3: $$\frac{9}{10}\left(p + 90\right) = \frac{9}{10}p + 81$$ pages

We know that Robbie read 229 pages in total over the course of 3 days, so we can create and solve an equation of this situation.

$$p + \left(p + 90\right) + \left(\frac{9}{10}p + 81\right) = 229 \\ 2p + \frac{9}{10}p+ 171 = 229 \\ \frac{29}{10}p = 58 \\ p = 20$$

In other words, Robbie read 20 pages on Day 1.

Aug 9, 2023