1.1 Integers and Rational Numbers

www.ck12.org Chapter 1. Arithmetic ReviewWhen Keisha arrives, Ms. Thompson is already hard at work. She tells Keisha that there are new baby birds in therescue. Three of the birds have each given birth to five baby birds. Keisha can’t help grinning as she walks around.She can hear the babies chirping. In fact, it sounds like they are everywhere.“It certainly sounds like a lot more babies,” Keisha says.“Yes,” Ms. Thompson agrees. “We also released two birds yesterday.”“That is great news,” Keisha says smiling.“Yes, but we also found three new injured birds. Our population has changed again.”“I see,” Keisha adds, “That is 256 + 3 × 5 − 2 + 3 that equals 1296 birds, I think. I’m not sure, that doesn’t seemright.”We have an equation that Keisha wrote to represent the comings and goings of the birds in the aviary.Before we figure out if Keisha’s math is correct, let’s underline any important information in the problem.Wow, there is a lot going on. Here is what we have to work with.256 birds3 × 5 - three birds each gave birth to five baby birds1. birds were released2. injured birds were found.Since we started with 256 birds, that begins our equation. Then we can add in all of the pieces of the problem.256 + 3 × 5 − 2 + 3 =This is the same equation that Keisha came up with. Let’s look at her math.Keisha says, “That is 256 + 3 × 5 − 2 + 3 that equals 1296 birds, I think. I’m not sure, that doesn’t seem right.”It isn’t correct. Keisha forgot to use the order of operations.According to the order of operations, Keisha needed to multiply 3 × 5 BEFORE completing any of the otheroperations.Let’s look at that.256 + 3 × 5 − 2 + 3 =256 + 15 − 2 + 3 =256 + 13 + 3 =269 + 3 =272 =Now we can complete the addition and subtraction in order from left to right.256 + 15 − 2 + 3 = 272The new bird count in the aviary is 272 birds.29