81
Solving word problems with measures
Textbook: Part 3, lesson 81, pp. 40–42
GoalProblems with length, mass and volume; calculating with ml and l.
New words
quantity · kattalikjuice · sharbatglass · stakanpackage · qadoq
Explanation
Length (m), mass (kg) and volume (l) are quantities. We add and subtract only quantities of the same kind and in the same unit. In a multi-step problem, think what each step finds and solve step by step. In volume problems it is convenient to change everything to millilitres first and then give the answer in litres if needed.
Worked examples
A jug holds 2 l of lemonade. 250 ml was poured into each of 6 glasses: 2 000 − 6 × 250 = 2 000 − 1 500 = 500 ml is left.
A big carton equals 5 small cartons and a small carton is 200 ml: 200 × 5 = 1 000 ml = 1 l.
Class activity
“Juice party”: groups work out how many glasses and small and large cartons of juice a birthday needs and write a shopping list.
Practice
1
3 l 200 ml = ? ml
3200
2
From 5 l of juice, 250 ml was poured into each of 12 glasses. How many millilitres are left?
2000
3
14 boys and 16 girls came to a birthday. Each got 200 ml of juice. How many litres of juice were needed in total?
6
4
A small carton of juice is 200 ml; a large carton equals 5 small ones. How many large cartons replace 30 small cartons?
6
5
A family used 12 m³ of water in a month. How many litres is that?
12000