A certain type of mixture is prepared by mixing brand A at Rs.9 a kg. with brand B at Rs.4 a kg. If the mixture is worth Rs.7 a kg., how many kgs. of brand A are needed to make 40kgs. of the mixture?
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Brand A needed is 20kgs
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Brand A needed is 24kgs
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Brand A needed is 19kgs
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None of the above
B
Correct answer
Explanation
Use alligation: Brand A at Rs.9 and Brand B at Rs.4 to get mixture at Rs.7. The alligation chart gives ratios 3:2 (A:B). For 40 kg total, Brand A = 3/5 × 40 = 24 kg. Verification: (24×9 + 16×4) ÷ 40 = (216 + 64) ÷ 40 = 280 ÷ 40 = Rs.7/kg.