Mathematics
Grade 3
15 min
Estimate products - multiply by larger numbers
Estimate products - multiply by larger numbers
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1
Introduction & Learning Objectives
Learning Objectives
Define estimation and identify a 'friendly number' for a given fraction.
Round a two- or three-digit number to a nearby friendly number.
Estimate the product of a unit fraction and a larger whole number.
Use the language of estimation, such as 'about' or 'approximately', to describe their answer.
Solve simple word problems by estimating the fraction of a larger number.
Explain why estimation is a useful strategy for quick calculations.
Imagine you have a jar with 82 marbles and you want to give your friend about 1/4 of them. How can you figure out a close number without counting them one by one? 🔵
In this lesson, you will learn a super-fast math trick called estimation! We will learn how to make a smart guess to find a frac...
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Key Concepts & Vocabulary
TermDefinitionExample
EstimateTo make a smart guess that is close to the exact answer. We use estimation when we need an answer that is 'about' right.Instead of calculating 19 + 32, you can estimate that 20 + 30 = 50. The exact answer is 51, so 50 is a great estimate.
ProductThe answer you get when you multiply two or more numbers together.In 2 x 5 = 10, the number 10 is the product.
Unit FractionA fraction where the top number (the numerator) is 1. It represents one equal part of a whole.1/2, 1/3, and 1/8 are all unit fractions.
Friendly NumberA number that is easy to work with in your head, especially for division. It's often a multiple of another number in the problem.To find 1/4 of a number, friendly numbers are multiples of 4, like 40, 80, or 120, because they are easy...
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Core Formulas
The Estimation Steps
1. Look at the fraction. 2. Round the large number to a 'friendly' number. 3. Find the fraction of the friendly number.
Use these three steps to estimate the product of a fraction and a large number. A 'friendly' number is a multiple of the fraction's denominator.
Finding a Unit Fraction of a Number
To find 1/d of a number n, you calculate n ÷ d.
This formula shows that finding a unit fraction of a number is the same as dividing that number by the denominator.
4 more steps in this tutorial
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Challenging
You need to estimate 1/8 of a number. Your friend tells you the number is 'between 235 and 245'. What is the best possible estimate you can make?
A.About 20
B.About 40
C.About 30
D.About 240
Challenging
The estimated product of a unit fraction and a large number is 'about 40'. The unit fraction used was 1/3. Which of these original numbers is the MOST likely one that was estimated?
A.118
B.139
C.43
D.100
Challenging
A school has 358 students. About 1/4 of them ride the bus. About 1/9 of them walk to school. Approximately how many more students ride the bus than walk?
A.About 90
B.About 40
C.About 130
D.About 50
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