For Tonya's height, days before his 9th birthday, she grew up (in inches):
![51.5\text{ + 2.25 }](https://img.qammunity.org/2023/formulas/mathematics/college/g0wgxf6r6cbim6s982u8wx1jpgtboiljwy.png)
![51.5\text{ + 2.25 = 53.7}](https://img.qammunity.org/2023/formulas/mathematics/college/a5zyy83w44j68z55e7qy0dlexb001wemlc.png)
We are using significant digits. The last measure for height was 51.5. And the last measure was 2.25. However, we only have one digit in the decimal part for the first measure, and we need to use only one digit of the second measure. Thus, the final measure is 53.7 inches.