model 3 reducing & exceeding prices Section-Wise Topic Notes With Detailed Explanation And Example Questions

Answer: (b)

10 percent of Rs.837

= $10/100 × 837$ = Rs.83.7

Reduced per kg price

= $83.7/6.2$ = Rs.13.50

Reduced price per kg

= ${10 × 837}/{100 × 6.2}$ = Rs.13.50

Answer: (c)

Reduced price of 6.2kg of sugar

= 10% of Rs.1116 = Rs.111.6

Reduced price per kg

= Rs.$(111.6/6.2)$ = Rs.18

Using Rule 31,

New price = ${10 × 1116}/{100 × 6.2}$

= $1116/62$ = Rs.18

Answer: (d)

Let the original price of sugar be Rs.x/kg.

New price = Rs.${9x}/10$ /kg

$270/{{9x}/10} - 270/x =1$

$300/x - 270/x = 1 ⇒ 30/x = 1$ ⇒ x = Rs.30 /kg

Using Rule 31,

New price = ${10 × 270}/{100 × 1}$ = Rs.27

Let the original price be Rs. x

$x - {10x}/100 = 27 ⇒ {90x}/100 = 27$

$x = 2700/90$ ⇒ x = 30

∴ Original price = Rs.30 per kg.

Answer: (a)

Original price of sugar = Rs. x/kg. (let)

New price = Rs.${120x}/100$ per kg.

= Rs.${6x}/5$ per kg.

According to the question,

$120/x - 120/{{6x}/5} = 4$

$120/x - {120 × 5}/{6x}$ = 4

$120/x - 100/x$ = 4

$30/x - 25/x$ = 1

$5/x$ = 1 ⇒ x = Rs.5 per kg.

Answer: (d)

Required percentage increase = $x/{100 - x} × 100$

= $(20/{100 - 20}) × 100 = 20/80 × 100 = 25%$

Answer: (c)

Required percentage change

= $(10 - 20 + {10 × (-20)}/100)$%

= –12% Negative sign shows decrease.

Required percentage = $(10 - 20 - {10 × 20}/100)$

= (–10 – 2) = 12% decrease.