- A21
- B3 2/3
- C7
- D83
Step-by-Step Solution
The machine does . Undo the steps in reverse order: , then . (Dividing first gives , which is wrong.)
Answer: C) 7
Priya puts her secret number into the machine shown and gets the output. What was her number?
Class 7Simple EquationsSimple Equations
Key idea: Translating word problems into equations
Three steps:
1. **Pick a variable** for the unknown ('let be the number of …').
2. **Translate the words into an equation** using the operations the problem describes.
3. **Solve and answer in the original units.**
Example: 'Three times a number plus 7 equals 22. Find the number.'
Let = the number. Equation: . Solve: .
Answer: the number is 5.
1. **Pick a variable** for the unknown ('let be the number of …').
2. **Translate the words into an equation** using the operations the problem describes.
3. **Solve and answer in the original units.**
Example: 'Three times a number plus 7 equals 22. Find the number.'
Let = the number. Equation: . Solve: .
Answer: the number is 5.
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