85
Solving problems: the post office
Textbook Part 3, pp. 24–25
GoalTell addition problems from subtraction problems; find the shortest route; a logic puzzle.
New words
postman · pochtachiparcel · jo‘natmashortest route · eng qisqa yo‘l
Explanation
Read the problem and look at the question first: “in all”, “altogether” usually mean add; “left”, “how many more” usually mean subtract. To choose a route, add the times of each route’s sections and pick the smallest total.
Worked examples
A parcel travelled 5 days by plane and 5 days by train: 5 + 5 = 10 days.
A postman must deliver to 78 flats and has done 32: 78 − 32 = 46 left.
Class activity
Logic game: 3 doors (blue, yellow, green) and 3 letters. No letter goes to its own colour door; the yellow letter does not go to the middle door. Children place the letters.
Practice
1
Route A: 12 + 15 minutes. Route B: 20 + 4 minutes. Which is faster?
B (24 < 27)
2
78 − 32 = ?
46
3
The post office has 35 envelopes and 24 postcards. Total?
59
4
A postman delivered 41 of 65 newspapers. How many are left?
24