The shopkeeper offers 3 successive discounts on a washing machine that costs Rs.58,000, so that the price gets reduced to Rs.42,000. If 5%,10% and x% are the respective discounts, find the value of x.

Correct option is C

Given : ​

Washing Machine  Coast : 58,000

After Discount : 42,000

After 3 succesive discounts of 5%, 10% and x%, the price is reduce to Rs. 42,000. 

Formula Used : 

Final Price = Original Price $$\times( 1-\frac{d1}{100}) \times (1-\frac{d2}{100})\times (1-\frac{d3}{100})$$​​

where d1 , d2 and d3 are successive discount.

Solution: 

After 3 succesive discounts of 5%, 10% and x%, the price is reduce to Rs. 42,000. 

So, 

The price after the first discount is :

​$$58000 \times\left(1-\frac{5}{100}\right)\times\left(1-\frac{10}{100}\right)\times\left(1-\frac{x}{100}\right)$$ = 42,000​

​$$58,000 ×\frac{95}{100 }×\frac{ 90}{100} ×\frac{ (100-x\%)}{100} = 42,000 \\ \ \\ {58 \times 95 \times 9} ×\frac{ (100-x\%)}{100} = 42,000\\ \ \\ (100-x\%) = 42,000\times\frac{100}{58 \times 95 \times 9} \\ \ \\100 - x \% = 84.69 \\ \ \\ x= 15.31$$​​

x =  15.3% 

Thus, the value of  x  is approximately = 15.3%.​​