Forming equations from situations
3 exam-style questions. Answers and the mark for each step are on the last page.
- Question 1
Zara thinks of a number. She doubles it and then adds 7. Her answer is 31.
(a) Form an equation and solve it to find Zara's number. You must show your working.
- Question 2
(a) A rectangular garden is 24 m long and 18 m wide. A path of uniform width is made inside all four edges. The remaining central rectangle has area 280 Work out the width of the path.
- Question 3
(a) A small auditorium has 330 seats arranged in rows. Each row has 3 more seats than the row immediately in front. The back row has three times as many seats as the front row. Work out the number of rows. You may use: sum of an arithmetic sequence = number of terms (first term + last term).
Answers and marks
Question 1
(a)
- M1 Forming .
- M1 Reaching .
- A1 The correct answer, .
Question 2
(a) m
- P1 Establishing or an equivalent valid method.
- P1 Establishing or an equivalent valid method.
- A1 Correct answer: m
Question 3
(a) rows
- P1 Establishing or an equivalent valid method.
- P1 Establishing or an equivalent valid method.
- P1 Establishing or an equivalent valid method.
- A1 Correct answer: rows