Category : 3rd Class

### Decimal Numbers and their Addition

A number with a decimal point is known as decimal number. The digit at right from decimal point is called whole part of the decimal number and digit at right side from the decimal point is called decimal part of the decimal number. In the decimal number 567.89, digits 567 are whole parts and digits 89 are decimal part. Place values of whole parts of decimal numbers are same as the place values of whole or natural numbers but the place values of decimal parts of the decimal numbers are read from left side and their place values are tenths, hundredth, thousandth, etc.

Three digits right after the decimal point are considered in the mathematical calculation.

The following steps are used for the addition of decimal numbers:

Step 1: Arrange the decimal numbers vertically, decimal numbers under decimal numbers and whole numbers under whole numbers.

Step 2: Add them starting from right of the decimal numbers.

Step 3: Carry over to the next addition.

Step 4: If carry is generated in the addition of tenth place digits then carry over to the addition of ones of the whole parts of the decimal numbers.

Step 5: Add the whole parts of the decimal numbers.

Add Rs 123. 25, Rs 85.60 and Rs 48.75.

111     -

123.25

85.60

+48.75

Rs257.60

The cost of 1 kg of potatoes is Rs 12.50 and the cost of 2 kg of tomatoes is Rs 56.75. How much money is paid on purchasing 1 kg of potatoes and 2 kg of tomatoes?

(a) Rs 69.75

(b) Rs 69.25

(c) Rs 60.50

(d) All of these

(e) None of these

Explanation

The total money paid

1

12.50

=56.75           = Rs 69.25.

69. 25

The addition of the terms 13a, 15b and 12a is:

(a) 25a+15b

(b) 15a + 15b

(c) Slab

(d) All of these

(e) None of these

Explanation 13 a + 12 a + 15 b = 25 a + 15 b.

If x = 1 and y = 2, then find the value of 2x + 3y.

(a) 5

(b) 8

(c) 7

(d) All of these

(e) None of these

.

There are 3 towns in a district. The population of the towns are 65786, 78976 and 32578. What is the total population of these three towns?

(a) 177340

(b) 177350

(c) 177800

(d) 207800

(e) None of these

Explanation 65786 + 78976 + 32578 = 177340.

There were 59 birds on the tree. 6 birds join them on the same tree and 6578 birds join them in the sky. What is the total number of birds in the swarm of the birds?

(a) 6645

(b) 6643

(c) 6640

(d) 6782

(e) None of these

Explanation The total number of birds = 59 + 6 + 6578 = 6643

Six pens cost Rs 72, 4 note books cost of Rs 32 and the cost of 7 books is Rs 124. Peter wants to purchase the given quantities of all the things. Find the total money he has to pay against the cost?

(a)Rs 228

(b) Rs236

(c) Rs237

(d) Rs248

(e) None of these

Explanation Total money paid by him = 72 + 32 + 124 = Rs 228.

Codi completes a work in 2 hours, Miriam and Peter complete the same work in 4 hours and 6 hours respectively. Add the total number of hours?

(a) 10

(b) 12

(c) 11

(d) All of these

(e) None of these

Explanation Total numbers of hours = 2 hours + 4 hours + 6 hours = 12 hours.

Priya spent 340 dollars to purchase a chair, 660 dollars for a table and 120 dollars for purchasing the table cloth. How much money did she spend for these items?

(a) Rs 1228

(b) Rs 1236

(c) Rs 1120

(d) All of these

(e) None of these

Explanation The total money spent = 340 + 660 + 120 = Rs 1120.

Priya bought 123 guavas, 130 oranges and 6 dozens bananas. After sometime she bought 220 more guavas. Find the total number of fruits bought by Priya.

(a) 545

(b) 536

(c) 537

(d) 548

(e) None of these

The total number of fruits bought by her = 123 + 130 + 72 + 220 = 545.

John bought 75 kg of wheat and 55 kg of rice. After sometime he again bought 3.5 kg of wheat and 5.5 kg of rice. The total quantities of rice and wheat bought by John is:

(a) 145kg

(b) 139kg

(c) 137kg

(d) 236kg

(e) None of these

Explanation:

The total quantities = 75 kg + 55 kg + 3.5 kg + 5.5 kg = 139 kg.

• Addition of two or more numbers starts from left or ones.
• The sum of more than two numbers is independent of the order in which the numbers are arranged.
• When zero is added to any number or a number is added to 0, the sum is the number itself.
• Carry of the addition of tenth place digits of two decimal numbers is added to the addition of ones of whole parts of the decimal numbers.
• Up to three digits right from the decimal point are usually considered.
• The sum of the numbers does not change on changing the groups of addends.
• A term with letter is added to the same terms or like terms.
• The addition of two same terms is the addition of their coefficient.
• The addition of two different or unlike terms is not possible.

• Addition by proper method was introduced by Chinese.
• Plus is a Latin word which means more.
• The letter P was used for the notation of plus in Europe.
• A positive number is also denoted by a positive sign behind the number i.e. +3.
• The terms, sum, plus, increase, total are the same terms.

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