A jar contains 8 white marbles, 10 orange marbles, and some red marbles. If the probability of picking a red marble is 1 in 4, then how many red marbles are there?
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Solution

Formula: 1 Mark
Calculations: 2 Marks
Answer: 1 Mark

Let the number of red marbles be x.
Total number of marbles = 8+10+x = 18+x

Given, the probability of picking a red marble is 1 in 4.
$\Rightarrow P (p i c k i n g r e d m a r b l e s) = \frac{x}{(8 + 10 + x)} = \frac{1}{4}$
$\Rightarrow 4 x = 8 + 10 + x \Rightarrow 3 x = 18 \Rightarrow x = 6$
Hence, there are 6 red marbles.

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A jar contains 8 white marbles, 10 orange marbles, and some red marbles. If the probability of picking a red marble is 1 in 4, then how many red marbles are there? [4 MARKS]

Formula: 1 Mark Calculations: 2 Marks Answer: 1 Mark Let the number of red marbles be x. Total number of marbles = 8+10+x = 18+x Given, the probability of picking a red marble is 1 in 4. ⇒P(picking red marbles)=x(8+10+x)=14 ⇒4x=8+10+x⇒3x=18⇒x=6 Hence, there are 6 red marbles.

A jar contains 8 white marbles, 10 orange marbles, and some red marbles. If the probability of picking a red marble is 1 in 4, then how many red marbles are there?
[4 MARKS]