You have 10 coins; 3 are gold, 7 are silver. If you randomly select 2, what is the probability they are both gold?
Category: Math · Difficulty: expert
Hint: Use combinations to calculate probabilities.
Answer
1/15
Explanation
The probability of choosing 2 gold coins from 3 is calculated as C(3,2)/C(10,2) = 3/45 = 1/15.
This is a expert math riddle — one of the harder riddles here. The answer is 1/15.
More Math riddles
- What is the result of adding 15 and 27?
- If you count from one to ten, how many 'fives' do you say?
- What is the area of a circle with a radius of 7?
- If an elevator has a weight limit of 1000 kg and it already has 400 kg, how much more weight can it take?
- If a car travels 80 km in 1 hour, how far will it travel in 2 hours?
- How many days are in a week?
- What do you call a number that can’t keep still? A roamin’ numeral! But what is the most famous one?
- What is the next leap year after 2020?