# Question

Source: on sponge

At first

20¢ → 49u (⅞ = 49/56)

50¢ → 7u

Total → 56u

Spent

20¢ → 14.80 ÷ 0.20 = 74

50¢ → 5/7 × 7u = 5u

Remaining

20¢ → (49u – 74)

50¢ → 2u

Total → (49u – 74) + 2u = (51u – 74)

Given: end quantity is ¼ of original

(51u – 74) = ¼ × 56u = 14u

37u = 74

u = 2

Remaining:

20¢ → (49u – 74) = 24

50¢ → 2u = 4

Amount left → (24 × 0.20) + (4 × 0.50) = \$6.80

0 Replies 2 Likes ✔Accepted Answer

14.80/20 = 74
20-cent coins : 49u – 74
50-cent coins : 7u – 5u = 2u
(1/4) x 56u = 14u
49u – 74 + 2u = 51u – 74 ——- 14u
1u ——- 74/(51 – 14) = 2
(49u – 74) x 0.20 + (2u x 0.50) = (49 x 2 – 74) x 0.20 + (2 x 2) x 0.50 = 6.80

Ans : \$6.80.

0 Replies 1 Like

\$14.80 of 20-cents –> 14.8/0.2 = 74 coins

20-cents coins        50-cents coins      Total

7                  :               1               :      8       (x7 so can get 5/7 of 50-cents coins)

At first               49u              :               7u            :    56u

Change                -74                            -5u

End                  49u-74                           2u                         14u  (1/4 of 56u left)

Equate: 49u – 74   + 2u  = 14u  –> 37u = 74  –> u = 2

Value left      (49×2-74)x0.2  +     (2×2)x0.5       = \$6.80#

or value left   (14-2)x2x0.2  +     (2×2)x0.5       = \$6.80#

0 Replies 1 Like