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1 There are some red counters and some blue counters in a bag. 4 There are 4 red counters and x blue counters in a bag.
The ratio of red counters to blue counters is 3:1 2 counters are removed from the bag at random.
1
Two counters are removed at random. The probability that both the counters taken are blue is
1 3
The probability that both the counters taken are blue is Work out the value of x.
20 (6 marks)
Work how many counters were in the bag before any counters were removed.
5 There are 5 red counters and x blue counters in a bag.
(5 marks)
2 counters are removed from the bag at random.
2 There are some red counters and some blue counters in a bag. 5
The probability that both the counters taken are red is
The ratio of red counters to blue counters is 4:1 33
Work out the value of x.
(7 marks)
Two counters are removed at random.
22 6 There are n counters in a bag.
The probability that both the counters taken are red is
35
Work how many blue counters are in the bag. 4 of the counters are red and the rest are blue.
(5 marks) Ross takes a counter from the bag at random and does not replace it.
He then takes another counter at random from the bag.
3 There are 5 red counters and y blue counters in a bag.
1
The probability that Ross takes two blue counters is
Imogen takes a counter from the bag at random. 3
She puts the counter back into the bag. (a) Show that n2 – 13n + 30 = 0 (5)
Imogen then takes another counter at random from the bag. (2)
(b) Find the value of n.
The probability that the first counter Imogen takes is red and the second (7 marks)
1
counter Imogen takes is red is 7 There are n counters in a bag.
9
Work how many blue counters are in the bag. 8 of the counters are red and the rest are blue.
(5 marks) Adam takes a counter from the bag at random and does not replace it.
He then takes another counter at random from the bag.
1
The probability that Adam takes two blue counters is
5
(a) Show that n2 – 21n + 90 = 0 (5)
(b) Find the value of n. (2)
(7 marks)
Grade 9 Probability Equation Questions
1 There are some red counters and some blue counters in a bag. 4 There are 4 red counters and x blue counters in a bag.
The ratio of red counters to blue counters is 3:1 2 counters are removed from the bag at random.
1
Two counters are removed at random. The probability that both the counters taken are blue is
1 3
The probability that both the counters taken are blue is Work out the value of x.
20 (6 marks)
Work how many counters were in the bag before any counters were removed.
5 There are 5 red counters and x blue counters in a bag.
(5 marks)
2 counters are removed from the bag at random.
2 There are some red counters and some blue counters in a bag. 5
The probability that both the counters taken are red is
The ratio of red counters to blue counters is 4:1 33
Work out the value of x.
(7 marks)
Two counters are removed at random.
22 6 There are n counters in a bag.
The probability that both the counters taken are red is
35
Work how many blue counters are in the bag. 4 of the counters are red and the rest are blue.
(5 marks) Ross takes a counter from the bag at random and does not replace it.
He then takes another counter at random from the bag.
3 There are 5 red counters and y blue counters in a bag.
1
The probability that Ross takes two blue counters is
Imogen takes a counter from the bag at random. 3
She puts the counter back into the bag. (a) Show that n2 – 13n + 30 = 0 (5)
Imogen then takes another counter at random from the bag. (2)
(b) Find the value of n.
The probability that the first counter Imogen takes is red and the second (7 marks)
1
counter Imogen takes is red is 7 There are n counters in a bag.
9
Work how many blue counters are in the bag. 8 of the counters are red and the rest are blue.
(5 marks) Adam takes a counter from the bag at random and does not replace it.
He then takes another counter at random from the bag.
1
The probability that Adam takes two blue counters is
5
(a) Show that n2 – 21n + 90 = 0 (5)
(b) Find the value of n. (2)
(7 marks)
Grade 9 Probability Equation Questions
