Q8. An industrial process produces a certain amount of metal from a given amount of ore. The graph shows the production rate:
 Use the graph to find: (a) How much metal is produced from 4 tonnes of ore? (b) How much ore is needed to produce 120kg of metal?
(a) - answer and commentary We can read off the graph in both directions. It helps to draw vertical and horizontal arrows to make the reading accurate. Notice there is no marker saying 120kg on the metal scale, buit it is going up in 10's, so it is easy enough to see.
 So we read off: 4 tonnes of ore produces 170kg of metal.
Answer: 170kg (b) - answer and commentary 120kg of metal needs 2.8 tonnes of ore (There are 5 intervals between 2 tonnes and 3 tonnes so it must go up 2.0, 2.2, 2.4, 2.6, 2.8, 3.0) Answer: 2.8 tonnes. Next question
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