Intermediate November 2020 Unit 2 Q3
3. Identical rods can be placed end to end, as shown below.
Each rod is 17·5 cm long.
How many of these rods can be placed, in this way, between two points 4 metres apart? [4]
Number of rods = ……………………
| Scheme | Marks | Comments |
|---|---|---|
| \(\dfrac{400}{17{\cdot}5}\) or \(\dfrac{4}{0{\cdot}175}\) | M2 | M1 if incorrect place value (in either length). Digits 228….. implies M1. |
| = 22·8(….) or 22·9 | A1 | C.A.O. |
| (Number of rods =) 22 | B1 | FT if of equivalent difficulty. (i.e. ‘their 22·8’ must be greater than 1 AND their 1st decimal place number greater than or equal to 5.) Answer of 22 gains all 4 marks. Unsupported answer of 23 gains M2A0B0. |
Alternative method (trial and improvement)
| Scheme | Marks | Comments |
|---|---|---|
| Working with a multiple of 17·5 or 0·175. (n × 17·5 or n × 0·175) | S1 | Award this S1 only if n > 2 and n ≠ 4 and n ≠ 400. |
| 22 × 17·5 (= 385) or 22 × 0·175 (= 3·85) | B1 | This implies previous S1. |
| 23 × 17·5 (= 402·5) or 23 × 0·175 (= 4·025) | B1 | This implies previous S1 and previous B1 if 402·5 seen. |
| (Number of rods =) 22 | B1 | Must be seen in answer space or unambiguously identified (not simply embedded). Answer of 22 gains all 4 marks. Unsupported answer of 23 gains S1B0B1B0. |