A bag contains 7 red discs, 5 green discs and 2 pink discs. Helen adds 9 green discs and some pink discs to the discs already in the bag. The probability of taking a green disc is now $$$\frac{2}{7}$$$. Find the number of pink discs that Helen added to the bag.

Mathematics

IGCSE&ALevel

CAIE

Exam No：0580_w20_qp_23 Year：2020 Question No：11(b)

Answer:

Knowledge points:

E2.5.1 Derive and solve linear equations in one unknown

E2.5.2 Derive and solve simultaneous linear equations in two unknowns.

E2.5.3 Derive and solve simultaneous equations, involving one linear and one quadratic.

E2.5.4 Derive and solve quadratic equations by factorisation, completing the square and by use of the formula.

E2.5.5 Derive and solve linear inequalities. (Including representing and interpreting inequalities on a number line.) (Interpretation of results may be required.)

E8.1 Calculate the probability of a single event as either a fraction, decimal or percentage. (Problems could be set involving extracting information from tables or graphs.)

A bag contains 7 red discs, 5 green discs and 2 pink discs. Helen adds 9 green discs and some pink discs to the discs already in the bag. The probability of taking a green disc is now $$\(\frac{2}{7}\)$$. Find the number of pink discs that Helen added to the bag.

Answer:

Knowledge points:

Solution:

A bag contains 7 red discs, 5 green discs and 2 pink discs. Helen adds 9 green discs and some pink discs to the discs already in the bag. The probability of taking a green disc is now $$\(\frac{2}{7}\)$$. Find the number of pink discs that Helen added to the bag.

Answer:

Knowledge points:

Solution:

Related Question