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

Answer: (c)

Original price of article = Rs.x per kg.

New price = Rs.${79x}/100$ per kg

$100/{{79x}/100} - 100/x = 3$

$10000/{79x} - 100/x = 3$

${10000 - 7900}/{79x} = 3$

$2100/{79x} = 3$

$700/{79x} = 1$

$79x = 700 ⇒ x = 700/79$

New price

= ${79x}/100 = 79/100 × 700/79$ = Rs.7 per kg

Using Rule 31,

Reduced price per kg. = ${21 × 100}/{100 × 3}$ = Rs.7

Answer: (b)

Original price of building = Rs. 100 (let)

Its price in 2001 = Rs. 80

Its price in 2002 = Rs. 60

Required percentage decrease = $({80 - 60}/80) × 100$

= $200/8 = 25%$

Answer: (d)

Required percent = $x/{100 + x} × 100$

where x = 60%

= $60/160 × 100 = 75/2 = 37{1}/2$%

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)

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: (b)

The original price of 1 egg = Rs.x

Present price = Rs.$3/2x$

$24/x - 24/{{3x}/2} = 4$

$24/x(1 - 2/3) = 4$

$8/x = 4 ⇒ x = 2$

Present price of eggs per dozen

= $12 × 3/2 × 2 = Rs.36$

Using Rule 31,

New price = ${50 × 24}/{100 × {4/12}}$ = Rs.36