Let us Know: Other words denoting estimates are 'About', 'Approximate', 'nearby', ……….

__UNIT−2__

__NUMBERS__

** **

__Estimation__

** **

**Situation 1**

There
are two bunches of grapes find the number of grapes in bunch ‘A’ and bunch ‘B’
without counting it.

Number of grapes in bunch ‘A’ __110__

Number of grapes in bunch ‘B’ __60__

Then count the exact number of grapes
and note it.

Exact number of grapes in bunch ‘A’ __118__

Exact number of grapes in bunch ‘B’ __64__

**Situation 2**

The estimated bus fare for a trip from
trichy to Chennai is ₹ 300. The Exact bus fare is ₹ 286

Therefore, the value which is nearest
to the correct value is called its estimated value.

The symbol for estimate is

** **

**Let us
Know: **Other words denoting estimates are
'About', 'Approximate', 'nearby', ……….

**Activity 1**

**Fill and
enjoy (individual)**

__Able to estimate a number upto two digit__

Estimating a number to our desired
number is called estimation.

To estimate a number, first underline
the digit that is to be estimated. If the underlined digit is less than 5 then
the number should be rounded down to the nearest underlined digit.

For example, when we estimate 64 to
its nearest Tens place the number have to be rounded down to 60.

If the underlined digit is greater
than or equal to 5, then the number should be rounded upto the nearest
underlined digit.

For example, when we estimate 65 to
its nearest Tens place the number have to be rounded upto 70.

__Example
2.1__

Estimate
48 to its nearest Tens place.

**Solution**

Estimating
4** 8** to its nearest Tens place,
we get 50.

Since
the unit place is 8, which is greater than 5, the number have to be rounded
upto 50.

Therefore,
48 ≅ 50.

__Example
2.2__

Estimate
74 to its nearest Tens place.

**Solution**

Estimating
7** 4** to its nearest Tens place,
we get 70.

Since
the unit place is 4, which is less than 5, the number have to be rounded down
to 70.

Therefore,
74 ≅ 70.

__Example
2.3__

Estimate
144 to its nearest Tens place.

**Solution**

Estimating
14** 4** to its nearest Tens
place, we get 140.

Since
the unit place is 4, which is less than 5, the number have to be rounded down
to 140.

Therefore,
144 ≅ 140.

__Example
2.4__

Estimate
155 to its nearest Tens place.

**Solution**

Estimating
15** 5** to its nearest Tens
place, we get 160.

Since
the unit place is 5, which is equal to 5, the number have to be rounded upto
160.

Therefore,
155 ≅ 160.

** **

__Able to estimate sums, differences products and quotients up to
two digit numbers.__

** **

__Example
2.5__

If
the cost of 1 kg apple is ₹ 95 and the cost of 1 kg Guava is ₹ 48 then estimate
their cost nearest to Tens place and find their sum. Also, find the difference
between the estimated sum and actual sum.

**Solution**

Difference
between estimated value and actual value
= Estimated value – Actual value

=
150 − 143

= ₹ 7

** **

__Example
2.6__

If
the cost of a note book is ₹ 42 and the cost of a pen is ₹ 27, then estimate
their cost nearest to Tens place and find their difference. Also, find the
difference between the estimated value and actual value.

**Solution**

Difference
between estimated value and actual value = Actual value – Estimated value

=
15−10

= ₹ 5

** **

**Try this**

Write down the estimated value of numbers and find their sum.
Also, find the difference of their sum.

** **

__Example
2.7__

If
the cost of 1 metre cloth is ₹ 86, then estimate its cost nearest to Tens place
and find the cost of 5 metre cloth.

**Solution **

Therefore,
the cost of 5 metre cloth is ₹ 450

__Example
2.8__

If
the cost of 3 kg potato is ₹ 63, then estimate its cost nearest to Tens place
and find the cost of 1 kg potato.

**Solution **

Therefore,
the cost of 1 kg potato is ₹20

**Try this**

Write down the estimated value of numbers and divide. Then find
the difference between estimated value and actual value.

Tags : Numbers | Term 3 Chapter 2 | 5th Maths , 5th Maths : Term 3 Unit 2 : Numbers

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail

5th Maths : Term 3 Unit 2 : Numbers : Estimation | Numbers | Term 3 Chapter 2 | 5th Maths

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