A skip on a building site is emptied and refilled several times in a day. It is filled with \(2.4\) tonnes of rubble, then \(1.1\) tonnes are removed for re...
Question 1 Report
A skip on a building site is emptied and refilled several times in a day. It is filled with \(2.4\) tonnes of rubble, then \(1.1\) tonnes are removed for recycling. The skip now holds \(3.6\) tonnes.
- Work out the net change in the mass of rubble in the skip. (1)
- Find the mass of rubble in the skip before it was filled. (2)
Answer Details
This question tests finding a net change between two decimal quantities and reversing it to find an earlier value.
- (a) [1] The skip gains \(2.4\) tonnes and then loses \(1.1\) tonnes, so the net change is \[2.4 - 1.1 = 1.3\] tonnes.
- (b) [2] The mass before filling equals the current mass minus the net change: \[3.6 - 1.3 = 2.3\] The skip held \(2.3\) tonnes of rubble before it was filled.
Working with decimals follows exactly the same directed-number reasoning as whole numbers; align the decimal points carefully when subtracting.
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