WORD PROBLEMS INVOLVING DECIMALS

Problem 1 :

Benjamin fills his car with 50 liters of petrol. How much does it cost him if petrol is selling at 94.6 cents per liter?

Solution :

Quantity of petrol filled = 50 liters

Cost of 1 liter petrol = 94.6

Cost of 50 liters petrol = 94.6 × 50

= 4730 cents

Converting it into dollars, we get

= 4730/100

= $47.30

Problem 2 :

Potting mix sells at $3.80 per kg. How much would a 3.5 kg bag of potting mix cost?

Solution :

Cost of 1 kg potting mix = 3.80 kg

Cost of 3.5 kg potting mix = 3.5 × 3.80

= 13.3 kg

Problem 3 :

The sweet shop sells licorice at $9.40 per kg. How much would 250 g of licorice cost?

Solution :

Cost of 1 kg licorice = $9.40

1 g = 0.001 kg

250 g = 0.25 kg

Cost of 0.25 kg licorice = 0.25 × 9.40

= $2.35

Problem 4 :

The cost of electricity is 43.4 cents per kilowatt for each hour. What would:

i)  500 kilowatts of electricity cost for one hour

ii)  It cost to burn a 60 watt globe for 10 hours?

Solution :

i)  Cost of electricity for one hour = 43.4 cents per kilowatt

= 43.4/100

= $0.434

Cost of 500 kilowatts of electricity

= 0.434 × 500

= $217

ii)  60 watt

Cost of 1 kilowatt = 0.434

1000 watt = 1 kilowatt

Cost of 1 watt = 0.434/1000

Cost of 60 watt = 60 x (0.434/1000) 

Cost for 10 hours = 60 x 10 x (0.434/1000) 

= 0.26

So, approximately 26 cents.

Problem 5 :

At a milk processing factory, cartons are filled from large refrigerated tanks that each hold 8400 liters. How many 600 mL cartons can be filled from one tank?

Solution :

Capacity of refrigerated tank = 8400 liters

1 liter = 1000 ml

8400 liter = 8400 × 1000

= 8400 × 1000/600

= 1000 × 14

= 14000 cartons

Problem 6 :

A large mixer at a bakery holds 0.75 tones of dough. How many bread rolls, each of mass 150 g, can be made from the dough in the mixer?

Solution :

1 tone = 1000 kg = 1000000 g

0.75 tones = 750 kg = 750000 g

= 750000/150

= 5000 bread rolls

Problem 7 :

How many dozen bottles of wine can be filled from a 9000 liter fermentation tank if each bottle holds 750 mL?

Solution :

Total bottles filled = 9000 liter

1 liter = 1000 ml

9000 liter = 9000 × 1000

= 9000000 ml

Number of cans = 9000000/750

= 12000

1 dozen = 12 items

= 12000/12

= 1000 dozen bottles

Problem 8 :

A trophy store wishes to make brass medallions, each of mass 17.5 g, from 140 kg of brass. How many medallions can be made?

Solution :

1kg = 1000 g

140 kg = 140 × 1000

= 140000 g

Number of medallions = 140000/17.5

= 8000 medallions