Answer:

Step-by-step explanation:

ENS

Estimating Sums

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There are approximately 120 cookies.

The actual number of cookies is 122.

The estimate differs from the actual by 2.

2. There are 275 students in class IVth and 238 students in class Vth. Estimate the total number of students in the two classes.

W

There are approximately 500 students.  

The estimate differs from the actual by 13.  

Estimating Difference:

Example on Estimating Difference:

The school library has 284 science books and 268 social sciences books.

Estimate the difference in the number of books.

Rounded to TENS

Estimating Difference

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The difference is approximately 20 books.

The estimate differs from the actual number by 4.

Rounded to HUNDREDS

Rounded nNumbers

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In this case, rounding number to hundreds will not be meaningful as the difference will be 0.

Examples on estimating sums and differences of the numbers:

1. The number of students in Classes III, IV and V are 154,129 and 118. Estimate the total number of students in the three classes taken together.

Solution:

The rounded numbers are used to estimate.

So         154     ⇒     200     being more than 150

           129     ⇒     100     being less than 150

           118     ⇒     100     being less than 150

                            400     So total number as estimated is 400

[Note: Actual number is 401, which is one more than 400]

Answer: 400

2. There are 479 girls and 729 boys in a school. Estimate the total number of students in the school.

Solution:

For estimation the numbers may be taken to the nearest ten or hundred.

(i)         479     ⇒     480

           729     ⇒     730

         1208     ⇒     1210  

[Note: The estimated number is 1210 which is 2 more than the actual number]

(ii)         479     ⇒      500

           729      ⇒      700

         1208      ⇒     1200  

We use the rounded numbers for estimation.

           216     ⇒      220

          - 196     ⇒     200

              20     ⇒       20  

The estimated difference in number of pages is 20.

The actual difference is also 20.

Related Concept

● Addition

● Word Prction

● Estimating Sums and Differences

● Find the Missing Digits

● Multiplication

● Multiply a Number by a 2-Digit Number

● Multiplication of a Number by a 3-Digit Number

● Multiply a Number

● Estimating Products

● Word Problems on Multiplication

● Dividing Numbers

● Estimating the Quotient

● Division by Two-Digit Numbers

● Word Problems on Division

4th Grade Math Activities

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