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大師請教路!!!----數學---F.1
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發問:
請教我數學!!!Plz1)Mrs Lee bought tw type of lipsticks for $240. Type A costs $45 each and Type B coasts $80 each. If she bought 7 lipsticks altogether, how many lipsticks of each type did she buy?2)A has $15 more than B, and C has $8 less than A. How mush money does each person have if they have a totalof... 顯示更多 請教我數學!!!Plz 1)Mrs Lee bought tw type of lipsticks for $240. Type A costs $45 each and Type B coasts $80 each. If she bought 7 lipsticks altogether, how many lipsticks of each type did she buy? 2)A has $15 more than B, and C has $8 less than A. How mush money does each person have if they have a totalof $160? 3)There are some $5 coins and $2 coins in a saving box and the number of $5 coins is 6 more than that of the $2 coins .If the value of the coins is $128, find the total number of coins in the box. 更新: The answer is wrong!!!
最佳解答:
1)There should be a typo in the question since $240 cannot lead to meaningful answer. I changed the value to $420 instead... Let the number of lipstick A be x Let the number of lipstick B be y x + y = 7 … (1) 45x + 80y = 420 … (2) (1) => y = 7 – x Sub into (2), 45x + 80(7 – x) = 240 45x + 560 – 80x = 420 -35x = 420 – 560 = -140 x = 4 Mrs Lee bought 4 pieces of the $45 type, and 7 – 4 = 3 pieces of the $80 type. 2)Let the money that A,B C have are $A, $B and $C respectively A = B + 15 C = A – 8 = (B + 15) – 8 = B + 7 A + B + C = (B + 15) + B + (B + 7) = 160 3B + 22 = 160 3B = 138 B = 46 A = 46 + 15 = 61 C = 46 + 7 = 53 A has $61, B has $46 and C has $53 3)Let the number of $2 coins be x. Then the number of $5 coins = x + 6 Value of the coins = 2x + 5(x + 6) = 128 2x + 5x + 30 = 128 7x = 98 x = 14 So there are 14 "$2 coins" and 14 + 6 = 20 "$5 coins". 2009-08-19 20:39:50 補充： Which one is wrong??? (2) 61 - 46 = 15 61 - 53 = 8 61+46+53 = 160 2009-08-19 20:40:35 補充： (3) 20 - 14 = 6 2*14 + 5*20 = 128 2009-08-19 20:42:13 補充： (1) 7A0B = $315 6A1B = $350 5A2B = $385 4A3B= $420 3A4B = $455 2A5B = $490 1A6B = $525 0A7B = $560 No combination = $240!!!
其他解答:960E6207E048F01D
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