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

Answer: (a)

Original price of wheat = Rs.x /kg.

New price of wheat = Rs.${4x}/5 /kg$

$320/{{4x}/5} - 320/x = 5$

$320(5/{4x} - 1/x) = 5$

$320({5 - 4}/{4x}) = 5$

$320/{4x} = 5 ⇒ x = 320/{4 × 5} = Rs.16$

Using Rule 31,

New price = ${20 × 320}/{100 × 5}$

= $1280/100$ = Rs.12.8

Let the original price be Rs.x per kg.

$x - {20x}/100 = 12.8$

80x = 12.8 × 100

$x = 1280/80 ⇒ x = 16$ per kg.

Answer: (c)

Original rate = Rs.x per egg

New rate = Rs.${6x}/5$ per egg

$24/x - {24 × 5}/{6x} = 2$

$24/x - 20/x = 2$

$4/x = 2 ⇒ x = 2$

New rate = Rs.$12/5$ per egg.

Rate per dozen of eggs

= Rs.$(12/5 × 12)$ = Rs.28.80

Using Rule 31,

New price/present price

= ${20 × 24}/{100 × {2/12}}$ = Rs.28.80

Answer: (a)

Percentage decrease = $0.25/1.25 × 100 = 20%$

Answer: (c)

Required percent

= $\text"Decrease%"/{100 - \text"Decrease%"}$ × 100

= $10/{100 - 10} × 100 = 100/9 = 11{1}/9%$

Answer: (d)

Let original price of sugar be Rs. x per kg.

New price= Rs.$({120x}/100) =Rs.({6x}/5)$per kg.

According to the question,

$50/x - 50/{{6x}/5} = 2$

$50/x - {50 × 5}/{6x} = 2$

$50/x - 125/{3x} = 2$

${150 – 125}/{3x} = 2$

$6x = 25 ⇒ x = Rs.25/6$ kg.

Required quantity of sugar = $50/x$

= $50/{25/6} = {50 × 6}/25 = 12$kg.

Answer: (d)

Let the original price of apples be Rs.x/ dozen

New price = Rs.${4x}/5$ /dozen

$54/{{4x}/5} - 54/x = 10/12$

$54(5/{4x} - 1/x) = 5/6$

$54({5 - 4}/{4x}) = 5/6$

$54/{4x} =5/6 ⇒ 4x = {54 × 6}/5$

${4x}/5 = {54 × 6}/{5 × 5}$ = Rs.12.96

Using Rule 31,

Reduced price = ${20 × 54}/{100 × 10/12}$

= $1080/1000 × 12$ = Rs.12.96 per kg