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In your head, what's a quick and easy way to solve this?
99 + 35
Did you use a "friendlier" number like 100? That's the basic idea of estimation!
Estimation is your math superpower!
It's a way to make a quick, smart guess *before* you do the exact math. This helps you know if your final answer makes sense.
The main tool we use for estimation is Rounding.
The rule is simple:
If the digit is 0, 1, 2, 3, or 4, the number you're rounding to stays the same.
32 ➔ 30
If the digit is 5, 6, 7, 8, or 9, you round the number up.
37 ➔ 40
Let's solve: You have $48 and spend $29. About how much is left?
1. Estimate: Round first. $48 is about $50. $29 is about $30. So, 50 - 30 = 20.
2. Calculate: Find the exact answer. 48 - 29 = 19.
3. Compare: Is our exact answer (19) close to our estimate (20)? Yes! We can be confident.
You are buying groceries that cost $12.25 and $6.99. Use the 3 steps.
1. Estimate: $12.25 is about $12. $6.99 is about $7. So, $12 + $7 = $19.
2. Calculate: $12.25 + $6.99 = $19.24.
3. Compare: Our estimate of $19 is very close to $19.24. Perfect!
Round to the nearest ten:
Estimate the sum by rounding to the nearest ten:
Use the 3-Step Process for 152 - 39.
You drive 108 miles on Monday and 295 miles on Tuesday.
Estimate your total miles.
(Round to the nearest hundred first!)