![\"\"](\"/images/stars/stars-13.gif\")
You can put this solution on YOUR website!
A collection of 90 coins, pennies, nickels, and dimes, has a value of $2.85.
\n" ); document.write( " If there are twice as may pennies as there are nickels and dimes combined, how many pennies, dimes, and nickels are there?
\n" ); document.write( ":
\n" ); document.write( "p + n + d = 90
\n" ); document.write( ":
\n" ); document.write( ".01p + .05n + .10d = 2.85
\n" ); document.write( ":
\n" ); document.write( "\"there are twice as may pennies as there are nickels and dimes combined,\"
\n" ); document.write( "p = 2(n + d)
\n" ); document.write( "divide both sides by 2
\n" ); document.write( ".5p = n + d
\n" ); document.write( ".5p - n - d = 0; add to the 1st equation
\n" ); document.write( " p + n + d = 90
\n" ); document.write( "----------------------eliminates n and d find p
\n" ); document.write( "1.5p = 90
\n" ); document.write( "p =
\n" ); document.write( "p = 60 pennies
\n" ); document.write( ":
\n" ); document.write( "Rewrite the two equation using p=60
\n" ); document.write( "n + d = 30
\n" ); document.write( "n = (30-d)
\n" ); document.write( "and
\n" ); document.write( ".05n + .10d = 2.25
\n" ); document.write( "Substitute (30-d) for n
\n" ); document.write( ".05(30-d) + .10d = 2.25
\n" ); document.write( "1.5 - .05d + .10d = 2.25
\n" ); document.write( ".05d = 2.25 - 1.50
\n" ); document.write( "d =
\n" ); document.write( "d = 15 dimes
\n" ); document.write( "then obviously
\n" ); document.write( "n = 15 nickels
\n" ); document.write( ":
\n" ); document.write( ":
\n" ); document.write( "Check solutions by finding the total$
\n" ); document.write( ".01(60) + .05(15) + .10(15) =
\n" ); document.write( ".60 + .75 + 1.5 = 2.85, confirms our solution p=60; n=15; d=15 \n" ); document.write( "