Calculating probability as favourable outcomes ÷ total outcomes, expressing as fractions (and converting to decimals/percentages).
Where your child meets this in real life: Calculating chances with dice, cards, spinners, or selections
SEAGReady breaks calculate simple probabilities into 3 steps, taught in order so each skill builds on the last.
Calculate probability using favourable outcomes divided by total outcomes when the favourable outcome is directly stated
Calculate probability when favourable outcomes must be identified and counted based on a condition
Calculate P(not A) using the complement rule: P(not A) = 1 - P(A)
Three free sample questions from our calculate simple probabilities course. Every question comes with a full explanation, and hints that guide without giving the answer away.
A bag contains 2 red counters, 3 blue counters, and 5 yellow counters. Ciara picks one counter without looking. What is the probability she picks a blue counter?
Answer: A. 3/10
First, count the total counters: 2 + 3 + 5 = 10 counters. Blue counters = 3 (this is the favourable outcome). Using the probability formula: P(blue) = favourable outcomes / total outcomes = 3/10. The probability of picking blue is 3/10.
Stuck? Start here: First, count how many counters are in the bag altogether.
Cormac rolls a fair six-sided die numbered 1 to 6. What is the probability of rolling an even number?
Answer: A. 3/6
Even numbers from 1 to 6 are: 2, 4, 6. That's 3 favourable outcomes. Total possible outcomes = 6. P(even) = 3/6 = 1/2. The probability of rolling an even number is 3/6 (which simplifies to 1/2).
Stuck? Start here: First, list all the even numbers from 1 to 6.
The probability of rain tomorrow in Belfast is 3/5. What is the probability it will NOT rain tomorrow?
Answer: A. 2/5
P(rain) + P(not rain) = 1. P(not rain) = 1 - P(rain) = 1 - 3/5. Write 1 as 5/5: P(not rain) = 5/5 - 3/5 = 2/5. The probability it will NOT rain is 2/5.
Stuck? Start here: P(event) and P(not event) always add up to 1.
This is the exact interactive worked example your child sees in SEAGReady. Step through it and watch the method build up.
Aoife has a bag with 3 red counters, 2 blue counters, and 5 green counters. She picks one counter without looking.
What is the probability of picking a red counter?
P(red) = ?
Step 1 of 3
Aoife has a bag with 3 red counters, 2 blue counters, and 5 green counters. She picks one counter without looking.
What is the probability of picking a red counter?
The probability of picking a red counter is ³⁄₁₀.
The key insight: Probability is always favourable on top, total on the bottom!
Watch out: P(red) = ¹⁰⁄₃ (total on top). The favourable outcomes must be the numerator, total outcomes the denominator.
These are the misconceptions we see most often in calculate simple probabilities, including the ones our practice questions are specifically designed to catch.
Struggling with calculate simple probabilities? The real gap is often in one of these earlier topics.
SEAGReady finds the exact step where your child gets stuck, teaches it with worked examples like the one above, and brings it back for review so it sticks.