Given:
A sells motorboat to B at = 18% loss
B sells it to C at = 25% profit.
C after refurbishing sold it to D at = 80% profit.
Concept used:
Let C.P. = Cost price and S.P. = Selling price then,
Loss% = [(CP - SP) / CP] × 100
Profit% = [(S.P. - C.P.) / C.P.] × 100
Solution:
Let the cost price for A be Rs.x.
S.P. of A can be calculated using above formula as:
Loss% = [(CP - SP) / CP] × 100
18 = [(x - S.P.) / x] × 100
18 / 100 = (x - S.P.) / x
18x = 100 × (x - S.P.)
18x = 100x - 100 × S.P.
100 × S.P. = 100x - 18x
S.P. = 82x / 100
S.P. = 41x / 50.
This becomes the C.P. for B.
S.P. for B can be calculated as:
Profit% = [(S.P. - C.P.) / C.P.] × 100
\(25 = \left(\dfrac{S.P. - \dfrac{41x}{50}}{\dfrac{41x}{50}}\right) \times 100 \)
\(\dfrac{25}{100} = \left (\dfrac{\dfrac{50\times S.P. - 41x}{50}}{\dfrac{41x}{50}}\right)\)
1 / 4 = (50 × S.P. - 41x) / 41x
41x = 200 × S.P. - 164x
S.P. = 205x / 200
S.P. = 41x / 40.
This becomes C.P. for C.
Now, C sells the motorbike to D at a profit of 80%, so S.P. for C:
Profit% = [(S.P. - C.P.) / C.P.] × 100
\(80 = \left(\dfrac{S.P. - \dfrac{41x}{40}}{\dfrac{41x}{40}}\right) \times 100\)
\(\dfrac{80}{100} = \left (\dfrac{\dfrac{40\times S.P. - 41x}{40}}{\dfrac{41x}{40}}\right)\)
4 / 5 = (40 × S.P. - 41x) / 41x
4 × 41x = 5 × (40 × S.P. - 41x)
164x = 200 × S.P. - 205x
369x = 200 × S.P.
S.P. = 369x / 200.
As D paid Rs. 36,531 for the motorbike, we get
369x / 200 = 36531
x = (36531 × 200) / 369
x = (4059 × 200) / 41
x = 99 × 200
x = 19800.
∴ Rs. 19800 is the cost price of A.
Alternate Method
Given:
A sells motorboat to B at = 18% loss
B sells it to C at = 25% profit.
C after refurbishing sold it to D at = 80% profit.
Concept used:
S.P. = C.P. + (Profit%) × C.P.
S.P. = C.P. - (Loss%) × C.P.
Solution:
Let the cost price (C.P.) for A be 100 units.
S.P. for A,
S.P. = C.P. - (Loss%) × C.P.
S.P. = 100 - (18 / 100) × 100
S.P. = 82.
This becomes C.P. for B.
S.P. for B,
S.P. = C.P. + (Profit%) × C.P.
S.P. = 82 + (25 / 100) × 82
S.P. = 82 + 2050 / 100
S.P. = 82 + 20.5
S.P. = 102.5.
This becomes C.P. for C.
S.P. for C,
S.P. = C.P. + (Profit%) × C.P.
S.P. = 102.5 + (80 / 100) × 102.5
S.P. = 102.5 + (4 / 5) × 102.5
S.P. = 102.5 + 4 × 20.5
S.P. = 102.5 + 82
S.P. = 184.5
This is the amount paid by D thus,
184.5 = 36531
1 = 198.
As the value of 1 unit is 198 and we assumed C.P. for A to be 100 units, we get
100 = 19800.
∴ Rs. 19800 is the cost price of A.