In 1 kg mixture of sand and iron, 20% is iron. How much sand

Question

In 1 kg mixture of sand and iron, 20% is iron. How much sand should be added so that the proportion of iron becomes 10%?

(a) 1kg 
(b) 200gms 
(c) 270gms 
(d) 1.8kg 
(e) 4.5kg 
(f) 500gms

Bunuel · Answer

There are 200 grams of iron in 1 kg (1,000 grams) of the mixture.

If we add x grams of sand, the total amount would be 1,000 + x grams of mixture and we need 200 grams of iron to be 10% of that: 0.1(1,000 + x) = 200 --> x = 1,000.

Answer: A.

Or: for 200 grams of iron to be 10 of the mixture, the mixture must be 2,000 grams, thus 2,000 - 1,000 = 1,000 grams of sand should be added.

Answer: A.

unceldolan · Answer

We have 1kg = 1000 grams of sand and iron. Iron is 20 % which means that the mixture consists of 200 grams iron and 800 grams sand.

Now, since the new mixture should contain 10 % iron, you need to find out, which amount in total is needed, so that 200 grams iron = 10 %. Since 200 grams is 10 % of 2000 grams, we need to add 1000 grams or 1kg of sand.

Answer A.

KarishmaB · Answer

You can also use the scale method using the proportion of iron:

wSand/wMix = (20 - 10)/(10 - 0) = 1:1

So in 1 kg of mix, you must add 1 kg of sand.

Answer (A)

vishwash · Answer

thanks for a cool question in the hot summers ( in india ) .. got to get a grip on these mixture problems... thanks to everyone for all the wonderful explainations

ydmuley · Answer

In 1 kg mixture of sand and iron, 20% is iron. How much sand should be added so that the proportion of iron becomes 10%?

Total Mixture = 1 Kg = 1000 Grams

Iron = 20% = 200 Grams

Sand = 80% = 800 Grams

We have make the 20% Iron to 10%

Which means we will make 200 Grams to 10% any additional sand which we are adding

200 = 10%(1000 + New Sand)

200 = 100 + 0.1 * New Sand

New Sand = 1000 Grams  = 1 Kg

Hence, Answer is A

bumpbot · Answer

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In 1 kg mixture of sand and iron, 20% is iron. How much sand

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In 1 kg mixture of sand and iron, 20% is iron. How much sand

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