Let's use everything we learned about estimation in the last lessons to solve some real-world problems together.
Jessie harvested 378 apples yesterday. The day before yesterday, he harvested 512 apples. About how many apples did Jessie harvest in the last two days?
We could to add the numbers.
378 + 512 = ?
But the word “about” gives us a clue that we only need an estimate.
To estimate means finding a number that’s not exact, but close enough to the original answer.
To estimate the sum of two numbers, we round the addends to their highest place values before adding.
What's 378 rounded to the nearest hundred? 🤔
Correct, 400.
What's 512 rounded to the nearest hundred? 🤔
500.
Now, we add these rounded numbers together.
400 + 500 = 900
Remember to write your answer as a sentence:
Jessie harvested about 900 tomatoes in the last two days. ✅
Let's try another example.
Bobby and Ross are reading the world's longest book. Bobby has already read 1,892 pages. Ross has already read 2,901 pages. About how many more pages did Ross read than Bobby?
What does the problem ask us to do?
We need to estimate the difference.
We don’t really need to find the actual answer, just a number close to it.
First, we round the minuend and subtrahend (the numbers we're subtracting from each other).
What's 2,901 rounded to the nearest thousand?
3,000.
What's 1,892 rounded to the nearest thousand?
2,000.
Let's subtract those rounded numbers.
3,000 – 2,000 = 1,000
Our final answer is:
Ross has read about 1,000 pages more than Bobby. ✅
Jenny’s office sends around 93 packages each day. Around how many packages does Jenny’s office send in 5 days?
The problem is asking us to estimate a product.
To estimate a product, we first round the biggest factor to its highest place value.
What is 93 rounded to the nearest Ten?
You’re right, it’s 90.
Now, we can multiply the rounded factor by 5.
Tip: We don't need to round the other factor, 5, because it's already easy enough. We can get a better estimate just leaving it alone.
90 × 5 = ?
Can you find the answer in your head?
The estimated product is 450.
Jenny’s office sends around 450 packages in 5 days. ✅
Great job learning how to solve estimation word problems.
Now, try the practice. You'll master the skill.