SOLUTION: How much sand must be added to 250 kg of a cement mixture that is 22% sand to have a mixture that is 25% sand?

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Question 509429: How much sand must be added to 250 kg of a cement mixture that is 22% sand to have a mixture that is 25% sand?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let x = kg of cement to be added
given:
+.22%2A250+=+55+ kg of sand initially
----------
+%28x+%2B+55%29+%2F+%28x+%2B+250%29+=+.25+
+x+%2B+55+=+.25%2A%28x+%2B+250%29+
+x+%2B+55+=+.25x+%2B+62.5+
+.75x+=+7.5+
+x+=+10+
10 kg of sand must be added
check:
+%28x+%2B+55%29+%2F+%28x+%2B+250%29+=+.25+
+%2810+%2B+55%29+%2F+%2810+%2B+250%29+=+.25+
+65+%2F+260+=+.25+
+65+=+65+
OK