MathAmigo

Probability of Single Events

Secondary 2 practice

Start free

Probability of Single Events practice questions

Secondary 2 topics, working towards the O-Level Mathematics 4052 syllabus. Every question below has a full worked solution.

When a student gets a question wrong in Math Amigo, it does not show the answer straight away. It reads the working, identifies the step that went wrong, and asks a question that points at the correction. The worked solution is there once a genuine attempt has been made.

Practise Probability of Single Events free

What this topic covers

Worked examples

Example 1

A box contains 11 red, 7 black, 11 green and 7 white counters. A counter is drawn at random. Find the probability of drawing a white or red counter. Give your answer as a fraction in its simplest form.
Show the worked solution
  • Total number of counters=11+7+11+7\text{Total number of counters} = 11 + 7 + 11 + 7
  • =36= 36
  • Number of favourable outcomes (white or red)=18\text{Number of favourable outcomes (white or red)} = 18
  • P(white or red)=1836P(\text{white or red}) = \frac{18}{36}
  • =12= \frac{1}{2}

Answer: 1/21/2

Example 2

A circle is divided into 55 sectors of different colours. The angles of the grey, red, orange and pink sectors are 95°95°, 125°125°, 70°70° and 35°35° respectively. Find the angle of the green sector.
Show the worked solution
  • Sum of known angles=95°+125°+70°+35°\text{Sum of known angles} = 95° + 125° + 70° + 35°
  • =325°= 325°
  • Angle of green sector=360°−325°\text{Angle of green sector} = 360° - 325°
  • =35°= 35°

Answer: 3535

Example 3

A box contains x orange marbles, (x+1)(x + 1) blue marbles and 77 purple marbles. A marble is drawn at random. The probability of drawing a blue marble is 512\frac{5}{12}. Find the value of x.
Show the worked solution
  • Total =x+(x+1)+7= x + (x + 1) + 7
  • =2x+8= 2x + 8
  • P(blue)=x+12x+8P(\text{blue}) = \frac{x + 1}{2x + 8}
  • x+12x+8=512\frac{x + 1}{2x + 8} = \frac{5}{12}
  • 12(x+1)=5(2x+8)cross multiply12(x + 1) = 5(2x + 8) \quad \scriptsize\textit{cross multiply}
  • 12x+12=10x+4012x + 12 = 10x + 40
  • 2x=282x = 28
  • x=14x = 14

Answer: 1414

Questions parents ask

Is it really free?

The free plan is permanent and does not ask for a card. It has daily limits on the AI feedback, and the paid plans lift them.

Which syllabus does this follow?

O-Level Mathematics (4052), for Singapore secondary students. Math Amigo covers Secondary 1 to 4, both O-Level Mathematics and Additional Mathematics.

Will it just show my child the answer?

No. On a wrong answer it looks at the working, points to the step that went wrong, and asks a question that helps the student find the correction. The full worked solution is available after a genuine attempt.

Other Secondary 2 topics