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2 math problems
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發問:
1. sailing with the current, a boat takes 3 hours to travel 48 miles. the return trip, against the current, takes 4 hours, find the average speed of the boat for the entire trip and the speed of the current.2. a coin bank contains nickles, dimes, and quarters totaling $5.45. if there are twice as many quarters as... 顯示更多 1. sailing with the current, a boat takes 3 hours to travel 48 miles. the return trip, against the current, takes 4 hours, find the average speed of the boat for the entire trip and the speed of the current. 2. a coin bank contains nickles, dimes, and quarters totaling $5.45. if there are twice as many quarters as dimes and 11 more nickles than quarters, how many of each coin are in the bank?
最佳解答:
1. Sailing with the current, a boat takes 3 hours to travel 48 miles. The return trip, against the current, takes 4 hours, find the average speed of the boat for the entire trip and the speed of the current. Sol: Suppose the speed of the boat is x mile/h, and the speed of current is y mile/h 3 * ( x ＋ y ) ＝ 48 x ＋ y ＝ 16 ...... ( 1 ) 4 * ( x － y ) ＝ 48 x － y ＝ 12 ....... ( 2 ) ( 1 ) ＋ ( 2 ) 2x ＝ 28 x ＝ 14 ( 1 ) － ( 2 ) 2y ＝ 4 y ＝ 2 Ans: boat ~ 14 mile/h; current 2 mile/h 2. A coin bank contains nickels, dimes, and quarters totaling $5.45. If there are twice as many quarters as dimes and 11 more nickels than quarters, how many of each coin are in the bank? Sol: Suppose the quantity of quarter is 2x therefore, dime is x and nickel is 2x ㊣ 11 0.25 * 2x ＋ 0.1x ＋ 0.05 * ( 2x ＋ 11 ) ＝ 5.45 0.5x ＋ 0.1x ＋ 0.1x ＋ 0.55 ＝ 5.45 0.7x ＝ 4.9 x ＝ 7 2x ＝ 14 2x ＋ 11 ＝ 25 Ans: quarter ~ 14; dime ~ 7; nickel ~ 25 Send me a letter and tell me which step if you don’t understand.
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