Last Wednesday, David withdrew an equal number of $10-notes and $20-notes from the bank. After spending 78 pieces of $10-notes and 10 pieces of $20-notes, the ratio of the remaining $10-notes to $20-notes became 3 : 7.
- How many $10-notes had he left?
- What was the total value of the notes which David withdrew from the bank?
| |
$10-notes |
$20-notes |
| Before |
3 u + 78 |
7 u + 10 |
| Change |
- 78 |
- 10 |
| After |
3 u |
7 u |
(a)
David withdrew an equal number of $10-notes and $20-notes from the bank. So, the number of notes of each type is the same.
7 u + 10 = 3 u + 78
7 u - 3 u = 78 - 10
4 u = 68
1 u = 68 ÷ 4 = 17
Number of $10 notes that David had left
= 3 u
= 3 x 17
= 51
(b)
Number of each type of notes that David withdrew
= 51 + 78
= 129
Value of one set of $10-note and 20-note
= 10 + 20
= $30
Total value of the notes that David withdrew
= 30 x 129
= $3870
Answer(s): (a) 51; (b) $3870
