Question 1157579
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An informal solution using logical reasoning and a bit of mental arithmetic....<br>
(1) 58 coins all dimes would have a value of $5.80.  The actual value is $9.85-$5.80 = $4.05 more.
(2) Exchanging a dime for a quarter keeps the number of coins at 58 and increases the total value by 15 cents.
(3) The number of dimes we need to exchange for quarters to make the additional $4.05 is 405/15 = 27.<br>
ANSWER:
27 quarters
58-27 = 31 dimes<br>
CHECK:
27(25)+31(10) = 675+310 = 985<br>