Probability Sum to 1 worksheet
10 GCSE practice questions with answers, free to print. Every sheet is generated, so you can make a fresh one whenever you need it.
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2 marks
A spinner can land on red, blue, green or yellow.
The table gives the probability of each colour.
Colour Red Blue Green Yellow Probability \(0.35\) \(0.15\) \(0.1\) ? Work out the probability that the spinner lands on yellow.
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3 marks
A bag contains 40 counters. 28 of the counters are black.
One counter is taken from the bag at random.
(a)Work out the probability that the counter is black. Give your answer as a fraction in its simplest form.
(b)Work out the probability that the counter is not black.
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3 marks
A bag contains counters. Some are yellow and the rest are green.
The probability that a counter taken at random is yellow is \(\frac{ 1 }{ 5 }\).
There are 9 counters that are yellow.
(a)Calculate how many counters there are altogether.
(b)Calculate how many counters are green.
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3 marks
A spinner can land on yellow, green or red only.
Priya writes down these probabilities.
Colour Probability yellow 0.3 green 0.4 red 0.4 (a)Explain how you can tell that Priya has made a mistake.
(b)State how much too big the total is.
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2 marks
A bag contains counters that are yellow, green, red or blue.
One counter is taken at random.
The probability that it is yellow is \(0.3\).
The probability that it is green is \(0.25\).
(a)Find the probability that the counter is yellow or green.
(b)Find the probability that the counter is neither yellow nor green.
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3 marks
A spinner can land on yellow, orange, green or purple.
The probability that it lands on yellow is \(0.45\).
The probability that it lands on orange is \(0.35\).
The probability that it lands on green is the same as the probability that it lands on purple.
Work out the probability that the spinner lands on purple.
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3 marks
A biased four-sided dice can land on 1, 2, 3 or 4.
The table shows the probability of each score.
Score 1 2 3 4 Probability \(\frac{7}{20}\) \(\frac{3}{10}\) \(\frac{1}{10}\) ? Work out the probability that the dice lands on 4. Give your answer as a fraction in its simplest form.
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3 marks
A spinner can land on red, green, blue or white.
The table gives the probability of each colour. The probabilities are not all written in the same way.
Colour Red Green Blue White Probability 0.05 25% \(\frac{1}{10}\) (a)Work out the probability that the spinner lands on white.
Give your answer as a decimal.
(b)Write down the colour the spinner is most likely to land on.
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4 marks
Find the probability that the spinner lands on orange.
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2 marks
A biased dice has some sections that are yellow and some that are green. It may also have sections of other colours.
The probability that it shows yellow is \(0.6\).
(a)Calculate the largest possible value of the probability that it shows green.
(b)Explain what would have to be true for the probability of green to take that largest value.
Answers
- \(0.4\)
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(a) \(\frac{7}{10}\)
(b) \(\frac{3}{10}\) -
(a) \(45\)
(b) \(36\) -
(a) The three probabilities add to \(1.1\), and the probabilities of all the outcomes must add to exactly 1.
(b) \(0.1\) -
(a) \(0.55\)
(b) \(0.45\) - \(0.1\)
- \(\frac{1}{4}\)
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(a) \(0.6\)
(b) White - \(0.42\)
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(a) \(0.4\)
(b) The biased dice would have to have no sections of any other colour, so that yellow and green were the only two outcomes.