Math in Focus Chapter 2: Mental Math and Estimation

In chapter 2 of Math in Focus, your child will learn about mental addition and subtraction, as well as estimation. Some of the skills your child will practice are:

• adding and subtracting 2-digit numbers mentally, with or without regrouping
• rounding numbers to estimate sums and differences using front-end estimation to estimate sums and differences

Vocabulary to Practice

Rounded is a term used in estimating numbers to the nearest ten, hundred, and so on.
2,436 is 2,400 when rounded to the nearest hundred.
An estimate is a number close to the exact number.
396 is 400 when rounded to the nearest hundred. 400 is an estimate. 
1,245 + 2,534 = 3,779
1,245 rounded to the nearest thousand is 1,000.
2,534 rounded to the nearest thousand is 3,000.
The estimated sum is 4,000. 3,779 is close to 4,000 so the answer is reasonable.
The leading digit in a number is the digit with the greatest place value. The leading digit for 2,475 is 2.
Front-end estimation uses leading digits to estimate sums and differences. 

At-Home Practice

This week, an important fact fluency packet was emailed home that connects to our previous blog post! Here is another activity to try:

The ability to estimate sums has numerous applications in everyday life! For example, have your child estimate the cost of your next shopping trip. Help him or her draw up a short family grocery shopping list. Then have your child write the prices of each item (wherever possible) by looking at advertised prices in the newspapers. Ensure the prices are in whole dollars as your child has not learned to estimate cost in compound units. Finally, have him or her estimate the total cost of the groceries.