Mathematical Reasoning
A bag holds red and yellow beads.
Question 1 · Multiple choice
Question
A bag holds red and yellow beads.
- There are 4 times as many yellow beads as red beads.
- When 6 yellow beads are removed, there are twice as many yellow beads as red beads.
Options
How many beads were in the bag to start?
- A.10
- B.12
- C.15
- D.18
- E.20
Correct answer
Explanation
Step 1: Set up expressions using one variable
Let the number of red beads = r.
Yellow beads = 4r (four times as many yellow as red).
Step 2: Use the second clue (remove 6 yellow beads)
After removing 6 yellow beads:
- Yellow left = 4r − 6
- Red stays at r
Now Tom has twice as many yellow as red:
4r − 6 = 2 × r
Step 3: Solve the equation
4r − 6 = 2r
4r − 2r = 6
2r = 6
r = 3 (there are 3 red beads)
Step 4: Find the total number of beads
Yellow beads = 4r = 4 × 3 = 12
Total beads = red + yellow = 3 + 12 = 15
Check: After removing 6 yellow: 12 − 6 = 6 yellow, 3 red. Is 6 = 2 × 3? Yes ✓
Answer: 15 beads in total