5106806
A hiker carries four packages with masses of \(0.85\,\text{kg}\), \(2.14\,\text{kg}\), \(3.15\,\text{kg}\), and \(1.86\,\text{kg}\).
Explain how to find the total mass mentally by making convenient pairs. Then give the total.
Hints
- Look closely at the hundredths digits.
- Which pairs add to a whole number?
- You do not need to add the four numbers in the order given.
Solution
1. Pair numbers that add to whole numbers: \(0.85 + 3.15\) and \(2.14 + 1.86\).
2. Evaluate the first pair: \(0.85 + 3.15 = 4.00\).
3. Evaluate the second pair: \(2.14 + 1.86 = 4.00\).
4. Add the pair sums: \(4.00\,\text{kg} + 4.00\,\text{kg} = 8.00\,\text{kg}\).
Answer
The total mass is \(8.00\,\text{kg}\). One efficient grouping is \((0.85 + 3.15) + (2.14 + 1.86) = 4.00 + 4.00 = 8.00\).
