Question Detail

If 16 toys cost 240, then what do 40 toys cost ?

Rs. 600
Rs. 620
Rs. 640
Rs. 660

Answer: Option C

Explanation:

Although we can first calculate the cost of one toy and then can multiply it with 40 to get the result.
but we will solve it with chain rule so that we can prepare ourself for other complex problems which we can solve easily by applying this rule.

Let the required cost be Rs. x
More toys means More Cost. (Direct Proportion)

\begin{aligned}
15:40 :: 240:x \\
=> x = \frac{240*40}{15} \\
=> x = 640
\end{aligned}

So 40 toys will cost Rs 640

1. If 16 toys cost 240, then what do 40 toys cost ?

Rs. 600
Rs. 620
Rs. 640
Rs. 660

Answer: Option C

Explanation:

2. If the cost of x metres of wire is d rupees, then what is the cost of y metres of wire at the same rate ?

xd
yd
yd/x
x/yd

Answer: Option C

3. In a dairy farm, 40 cows eat 40 bags of husk in 40 days. In how many days one cow will eat one bag of husk ?

34 days
40 days
46 days
50 days

Answer: Option B

Explanation:

Less Cows, More days (Indirect Proportion)
Less bags, Less days (Direct Proportion)

\begin{aligned}
\begin{bmatrix}Cows & 1 & 40 \\Bags & 40 & 1 \end{bmatrix} :: 40 : x \\
=> x * 40 * 1= 40 * 1 * 40 \\
=> x = 40
\end{aligned}

4. A flagstaff 17.5 metre high casts a shadow of length 40.25 metre. The height of building, which casts a shadow of length 28.75 metre under similar conditions will be :

12 metre
12.5 metre
13.5 metre
14 metre

Answer: Option B

Explanation:

Less shadow, Less Height (Direct Proportion)
So, let height of building be x metre
then,
\begin{aligned}
40.25 : 17.5 :: 28.75 : x \\

=> x = \frac{17.5*28.75}{40.25} \\
=> x = 12.5
\end{aligned}

So height of building should be 12.5 metre

5. An industrial loom weaves 0.128 metres of cloth every second. Approximately, how many seconds will it take for the loom to weave 25 metre of cloth ?

194 seconds
195 seconds
196 seconds
197 seconds

Answer: Option B

Explanation:

Let the time required by x seconds.
Then, More cloth means More time (Direct Proportion)
So,
\begin{aligned}
0.128 : 1 :: 25 : x
=> x = \frac{25*1}{0.128} \\
=> x = 195.31
\end{aligned}

So time will be approx 195 seconds

s 9 years ago

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Question Detail
If 16 toys cost 240, then what do 40 toys cost ?
Rs. 600
Rs. 620
Rs. 640
Rs. 660
Answer: Option C
Explanation:
Although we can first calculate the cost of one toy and then can multiply it with 40 to get the result.
but we will solve it with chain rule so that we can prepare ourself for
other complex problems which we can solve easily by applying this rule.
Let the required cost be Rs. x
More toys means More Cost. (Direct Proportion)
15:40::240:x=>x=240?4015=>x=640
your solution is incorrect
the correct answer is 600 calculate in prper way when question gives16 toy cost then how you will divide by 15
correct answer is:15:40::240:x=>x=240?40/16=>x=600
pravin c 10 years ago

For first question
Rs 240 for 16 toys so for 1 toy 240/16= 15
so for 40 toys 40*15 = 600.?
please confirm.
avinash 10 years ago

On first question you have given 16 toys cost 240 so 40 toys cost how much, but you have taken 15 toys cost is 240 so when we arrive at answer 600 according to question, you arrive at 640 please correct the question admin, there are some questions which have same mistakes in numbers, pls correct them admin bhai