Question

round each decimal to the nearest one. then add or subtract.

1. 2.8 + 1.3

round to the nearest one.
2.8 → ______
1.3 → ______
add.
____ + __ = ____
so, 2.8 + 1.3 is about ______

1. 5.98 - 1.03

round to the nearest one.
5.98 → ______
1.03 → ______
subtract.
____ - __ = ____
so, 5.98 - 1.03 is about ______

talk math
describe a real - world example when it might be appropriate to estimate rather than get the exact answer.

Explanation:

Problem 1: \(2.8 + 1.3\)

Step1: Round 2.8 to nearest one

To round \(2.8\) to the nearest one, we look at the tenths place. The digit in the tenths place is \(8\), which is greater than or equal to \(5\), so we round up the ones place. Thus, \(2.8\approx3\).

Step2: Round 1.3 to nearest one

For \(1.3\), the digit in the tenths place is \(3\), which is less than \(5\), so we round down the ones place. Thus, \(1.3\approx1\).

Step3: Add the rounded numbers

Now we add the rounded numbers: \(3 + 1 = 4\).

Step1: Round 5.98 to nearest one

To round \(5.98\) to the nearest one, we look at the tenths place. The digit in the tenths place is \(9\), which is greater than or equal to \(5\), so we round up the ones place. Thus, \(5.98\approx6\).

Step2: Round 1.03 to nearest one

For \(1.03\), the digit in the tenths place is \(0\), which is less than \(5\), so we round down the ones place. Thus, \(1.03\approx1\).

Step3: Subtract the rounded numbers

Now we subtract the rounded numbers: \(6 - 1 = 5\).

Suppose you are at a store and you want to quickly figure out how much two items might cost together. One item costs \(\$2.80\) and another costs \(\$1.30\). Instead of calculating the exact sum (\(2.8 + 1.3=4.1\)) to decide if you have enough money in your pocket (if you have around \(\$4\) or \(\$5\)), you can estimate by rounding to the nearest dollar. This gives you a quick idea of the total cost without having to do precise decimal addition.

Answer:

• \(2.8 \to 3\)
• \(1.3 \to 1\)
• \(3 + 1 = 4\)
• So, \(2.8 + 1.3\) is about \(4\)

Problem 2: \(5.98 - 1.03\)