Question

3. In January 2009, the price of rice in Singapore
was $x per kilogram. A food catering company
spent an average of $350 on rice each month.
(i) Write down an expression, in terms of x,
for the average amount of rice that this food
catering company ordered in January 2009.
In January 2012, the price of each kilogram of
rice had increased by 15 cents.
(ii) Given that the company continued to spend
$350 on rice each month, write down an
expression, in terms of x, for the average
amount of rice ordered in January 2012.
(iii) If the difference in the amount of rice ordered
is 30 kg, formulate an equation in x and show
that it reduces to 20x2 + 3x - 35 = 0.
iv) Hence, find the price of each kilogram of rice
in January 2012​

Answer 1

Answer:

3 answer is correct answer see nin Google

Answer 2

Answer:

(i)

Av. amount of rice ordered in Jan 2009 = 350x kg

(ii)

Av. amount of rice ordered in Jan 2012 = 350

x + 0.15 kg

(iii)

350

x – 350

x + 0.15

= 30

350(x + 0.15)

x(x + 0.15) – 350x

x(x + 0.15)

= 30

350(x + 0.15) – 350x

x(x + 0.15)

= 30

350(x + 0.15) – 350x = 30x(x + 0.15)

350x + 52.5 – 350x = 30x

2

+ 4.5x

30x

2

+ 4.5x – 52.5 = 0

60x

2

+ 9x – 105 = 0

20x

2

+ 3x – 35 = 0 (Shown)

(iv) 20x

2

+ 3x – 35 = 0

(4x – 5)(5x + 7) = 0

4x – 5 = 0 or 5x + 7 = 0

4x = 5 5x = –7

x = 1.25 x = –1 2

5 (rejected since

x > 0)

∴ Price per kilogram of rice in Jan 2012 = 1.25 + 0.15

= $1.40