In 50 gm alloy of gold and silver the gold is 80 % by weight. How much gold should be mixed with this alloy so that the weight of gold would become 95 %?
Correct answer: B. 150 gm
- A. 200 gm
- B. 150 gm
- C. 50 gm
- D. 10 gm
Explanation
Initially, gold weighs 80% of 50 g, so gold = 0.8 × 50 g = 40 g and silver = 10 g. If x g of gold is added, (40 g + x)/(50 g + x) = 0.95; solving gives 40 + x = 47.5 + 0.95x, so x = 150 g. Students may choose 50 g by ignoring that the added gold also increases the total alloy weight.
Last updated
About Percentages
Percentages express a quantity as parts per hundred and support calculations involving increases, decreases, discounts, commissions, taxes, and successive changes. Questions require distinguishing percentage change from percentage points and identifying the original value when a final value and its percentage change are given.
Practise Arithmetic
1,060 free Arithmetic MCQs from Mathematics, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Exams that ask Mathematics questions like this
Mathematics is on 67 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.
Related questions
10 % of the electorate did not cast their votes in an election between two candidates. 10 % of the votes polled were found invalid. The successful candidate got 54 % of the valid votes and won by a majority of 1620 votes. The number of voters enrolled on the voter's list was___________?
12.5 + 10 1/4 of 100 ÷ 10% of 10 = ____________?
16.66% of 33.33% of 66.66% of ? = 30
20% of 40 + ? % of 80 = 120
25% of 30% of 45% is equal to__________?