Edexcel IGCSE Math A 6.3.C basic probability calculations

Practise probability-calculation questions by forming favourable over total, then solving for missing counts when the probability is given.

Exam points

Calculate probability from favourable outcomes divided by the total number of outcomes.
Work backwards from a probability to find a missing number of counters, cars or items.
Compare probabilities across bags, boxes or spinners after converting to common values.

[Maximum number: 3]

Grace is going to spin the arrow on the spinner once.

The table below gives the probabilities that the spinner will land on red or on blue or on green.
The probability that the spinner will land on orange is 3 times the probability that the spinner will land on pink.

Figure for Question 6.3.C Theoretical probability question 1 — Edexcel IGCSE Math A Higher

Table for Question 6.3.C Theoretical probability question 1 — Edexcel IGCSE Math A Higher

Work out the probability that the spinner will land on orange.

Working:
1-(0.2+0.12+0.08)=0.6 $0.6\times\frac34=0.45$

Final answer:
0.45

M1 for a correct calculation or equation for the remaining probability. M1 for finding $\frac34$ of the remaining probability. A1 for 0.45, $\frac{9}{20}$ , $45\%$ , or $\frac{0.45}{1}$ .

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6.3.C Theoretical probability question 1