131
Expressions with letters
Textbook Part 4, pp. 42–43
GoalRead and write letter expressions; write an expression from a diagram.
New words
Latin letters · lotin harflarithe sum of … and … · … bilan … ning yig‘indisithe difference of … and … · … bilan … ning ayirmasi
Explanation
Letter expressions usually use Latin letters: a, b, c, d, k, m, x, y. Reading them: 3 + y is “the sum of 3 and y”; d − 15 is “the difference of d and 15”.
Worked examples
m bottles of juice and b bottles of lemonade were brought to a party: m + b bottles.
A lemonade has p spoons of sugar and a pack of biscuits t spoons. Amir had both: p + t spoons.
Class activity
In pairs: one says a letter expression (“the sum of x and 7”), the other writes it (x + 7), picks a number for x and works it out.
Practice
1
Write: “the sum of m and 12”.
m + 12
2
Read: 40 − b
the difference of 40 and b
3
Pattern: a = 2, 4, 6. The values of a + 10?
12, 14, 16
4
If x = 17, then x + 11 = ?
28