Fundamental Operations on Quantities with Different Units

Fundamental Operations on Quantities with Different Units

We can do the basic operations on the metric units as we do the decimal operations. Note that, measurements with the same unit can be added/ subtracted, but unlike units of measurements should be converted into like units and then they can be added / subtracted.

Example 8:

Saritha bought 6 m and 40 cm of cloth for herself and 3 m and 80 cm of cloth for her sister.  What was the total length of the cloth bought by her?

Solution:

Example 9:

Pradeep travels 4 km and 350 m to reach to the market, while Kandan travels 6 km and 200 m to reach to the same market from their houses.

How much distance does Kandan travel more than Pradeep?

Solution:

Kandan travelled 1 km and 850 m more than Pradeep.

Example 10:

 A child needs 100 g of vegetables per day. How many kg of vegetables will be needed for a school of strength 90.

Solution :

Total strength of the school                                     = 90

Weight of vegetables for each child per day           = 100 g

Total weight of vegetables for 90 children per day = 90 × 100 g

                                                                                    = 9000 g

                                                                                     = 9 kg vegetables need per day.

Example 11:

A bag contains 81 kg of sugar. If the shopkeeper made small packets of 750 g. each, then how many packets can be made from 81 kg of sugar?

Solution :

Quantity of sugar in the bag = 81 kg

Quantity of sugar in each packet = 750 g

Number of packets required = 81 kg ÷ 750 g

= 81 × 1000 g ÷ 750 g

= 81000 g ÷ 750 g

= 108

Think

1. Five kilograms of compost is needed for a coconut tree for every six months. How many kilograms of compost is needed for 50 such coconut trees for one and half years.?

Compost needed for a coconut tree for every six months = 5 kg.

Compost needed for 50 coconut trees for.

six months = 50 × 5 = 250 kg.

1 ½  years = 3 six months.

Compost needed for 50 coconut trees for

1 ½  years = 250 × 3 kg

= 750 kg.

Compost needed for 50 coconut trees for

1 ½  years =  750 kg. 

2. a. Is it correct: 4 m+3 cm = 7 m

False. 4 m + 3 cm = 400 cm + 3 cm = 403 cm

b. Can we add the following?

i) 6l + 7kg, ii) 3 m+5 l iii) 400 ml +300 g

No. We can not add measurements with unlike units.