document.write( "Question 1182797: When the price of an item was increased by sh.5, I bought 2 items fewer with sh.200.
\n" ); document.write( "what is the current price of the item? (It's a kcse question on 1994 pp1 no.16)
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Algebra.Com's Answer #812871 by greenestamps(13200)\"\" \"About 
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\n" ); document.write( "The number you can buy for sh.200 is 200 divided by the price.

\n" ); document.write( "The new price is sh.5 more than the old, so

\n" ); document.write( "let x = old price
\n" ); document.write( "then x+5 = new price

\n" ); document.write( "The number you can buy at the new price is 2 less than the number you could buy at the old price:

\n" ); document.write( "\"200%2F%28x%2B5%29+=+200%2Fx-2\"

\n" ); document.write( "Multiply everything by the least common denominator to clear fractions:

\n" ); document.write( "\"200%28x%29=200%28x%2B5%29-2%28x%28x%2B5%29%29\"
\n" ); document.write( "\"200x+=+200x%2B1000-2x%5E2-10x\"
\n" ); document.write( "\"2x%5E2%2B10x-1000+=+0\"
\n" ); document.write( "\"x%5E2%2B5x-500+=+0\"
\n" ); document.write( "\"%28x%2B25%29%28x-20%29+=+0\"

\n" ); document.write( "x=-25 or x=20; obviously the negative number makes no sense in the problem, so x=20.

\n" ); document.write( "The problem asks for the \"current\" (new) price, which is x+5=25.

\n" ); document.write( "ANSWER: The current price is sh.25.

\n" ); document.write( "Knowing how to solve the problem using formal algebra is important. But if this is a question on a competitive math exam, it's much faster to solve the problem informally.

\n" ); document.write( "To do that, write out (on paper if needed; or just in your mind) a list of all the pairs of positive integers whose product is 200; then look for two of those pairs in which one of the numbers differs by 2 and the other differs by 5.

\n" ); document.write( "1 * 200
\n" ); document.write( "2 * 100
\n" ); document.write( "4 * 50
\n" ); document.write( "5 * 40
\n" ); document.write( "8 * 25
\n" ); document.write( "10 * 20

\n" ); document.write( "Look at the last two pairs. The 8 and 10 differ by 2; the 25 and 20 differ by 5.

\n" ); document.write( "That gives you your answer. For sh.200, you can buy 8 of the items at sh.25 each or 10 of them at sh.20 each. So the current price, at which you can buy 2 fewer of the items than before, is sh.25.

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