<p>A box contains $\left( 6y+2 \right)$ red balls, $\left( 50-2y \right)$ blue balls and $3y$ yellow balls. </p>
<ol class="i-list"><li><div class="list-item-paragraph">Find an expression, in terms of $y$, for the total number of balls in the box. </div></li></ol>
<p>A ball is drawn at random from the box. </p>
<ol class="i-list" start="2"><li><div class="list-item-paragraph">Write down an expression, in terms of $y$, for the probability that the ball is red. </div></li><li><div class="list-item-paragraph">It is known that the probability when a red ball is drawn is $\frac{13}{40}$, find the value of $y$.</div></li></ol>

A box contains $\left( 6y+2 \right)$ red balls, $\left( 50-2y \right)$ blue balls and $3y$ yellow balls. 

Find an expression, in terms of $y$, for the total number of balls in the box. 

Write down an expression, in terms of $y$, for the probability that the ball is red. 

It is known that the probability when a red ball is drawn is $\frac{13}{40}$, find the value of $y$.

Balls in a Box: Variable-Based Probability

Balls in a Box: Variable-Based Probability

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