21
Review. Test 3
Textbook: pp. 54–55
GoalReview Chapter 3: sequences, algorithms, arrows and performers.
New words
review · takrorlashpath, route · yo‘lmistake · xatoto check · tekshirmoq
Explanation
Let us recall: the order of actions matters, and a wrong order changes the result. An algorithm has a name, a start, actions and an end. We steer a robot with arrows. A performer understands only its own commands. To find a mistake in an algorithm we check it by doing it step by step.
Worked examples
The robot is at the bottom left, the apple at the top right of a 3×3 field. The shortest algorithm: → → ↑ ↑ — 4 commands.
After ↑ ↑ → → ↓ ↓ ← ← the robot is back at its start, because up and down, and right and left, cancel each other.
Class activity
“Find the mistake”: the teacher reads a wrong algorithm (“Tea: add tea leaves, boil water, drink”). Children act the steps out, find the mistake and fix it.
Practice
1
On a 3×3 field, at least how many commands does a robot need to go from the bottom left square to the top right square?
4
2
A robot followed ↑ ↑ → → ↓ ↓ ← ←. Where is it?
on the start square
3
Algorithm: 1) add tea leaves, 2) boil water, 3) pour water. What is wrong and how to fix it?
The order is wrong: first boil water, then add tea leaves, then pour water