35
Problem solving (practice)
Textbook: Part 1, lesson 35, pp. 108–110
GoalPractise multi-step problems and problems that lead to equations.
New words
skein of yarn · kalavasum · yig‘indiequation · tenglamatable · jadval
Explanation
To solve a problem we use a table or a diagram. In a motion problem, for example, we put v, t and S in a table and find the unknown with a formula. If the sum of two numbers is known and one is n times the other, the smaller number = sum : (n + 1). We can also call the unknown x and write an equation.
Worked examples
The sum is 90 and one number is 5 times the other: the smaller is 90 : 6 = 15 and the larger is 75.
With v = 18 km/h and S = 90 km, t = 90 : 18 = 5 hours.
Class activity
“Table problem”: each group writes a problem with one empty cell in a v, t, S table and another group solves it.
Practice
1
Knitting one hat takes 3 skeins of yarn, each 120 m. How many metres of yarn are needed for 6 hats?
2160
2
The route is 90 km and the cyclist's speed is 18 km/h. How many hours does the ride take?
5
3
Solve (x − 24) × 3 = 360.
144
4
The sum of two numbers is 90 and one is 5 times the other. Find the smaller number.
15