標題:
有d數學問題唔識~(急!!!)
發問:
1.Pitt is 6 years old and his father is 46 years old now. After how many years will Pitt's age be 1 over 5 of his father's age?2.The cost of a desk is changed by +6% and it becomes $212 after the change. Find the original cost of the desk.3.Joe bought 12 footballs for $1000. If 2 footballs were lost... 顯示更多 1.Pitt is 6 years old and his father is 46 years old now. After how many years will Pitt's age be 1 over 5 of his father's age? 2.The cost of a desk is changed by +6% and it becomes $212 after the change. Find the original cost of the desk. 3.Joe bought 12 footballs for $1000. If 2 footballs were lost and he sold the remaining footballs at $110 each.What was the overall profit per cent? 4.If a shopkeeper sells a shirt at $220,then the profit per cent is 10%.What will be the shopkeeperreduces her profit per cent to 5%? 5.Lancy depoits $15000 in a bank gor 6 months. The bank pays simple interest at a certain interest rate. If Lancy will get the amount of $15600 at the end of the period,what is the interest rate per year? 6.Find the principal that will amount to $4650 after 2.5 years if simple interest is calculated at an interest rate of 6.5% p.a. 更新: 請列明成條橫式,,thZ=]
最佳解答:
1. Let x be the number of years later that Pitt's age will be 1 over 5 of his father's age (6+x)/(46+x) = 1/5 5(6+x) = 46+x 30+5x = 46+x 4x = 16 x = 4 So, after 4 years Pitt's age will be 1 over 5 of his father's age. 2. Let $x be the original cost of the desk x*(1+6%) = 212 1.06x = 212 x = 200 The original cost of the desk is $200. 3. Cost = $1000 Revenue = $110*(12-2) = $1100 Profit percentage = ($1100-$1000)/$1000*100% = 10% 4. cost = $220/(1+10%) = $200 new selling price = $200*(1+5%) = $210 new profit = $210-$200 = $10 5. interest = $15600-$15000 = $600 principal*interest rate(per annual)*time(in year) = interest Let r be the interest rate 15000*r*(6/12) = 600 r = 0.08 (or 8%) The interest rate is 8%. 6. Let $P be the principal P*0.065*2.5 = 4650-P P*(1+0.065*2.5) = 4650 1.1625P = 4650 P = 4000 The principal is $4000.
2. 212*(1-6%) = 199.28 3. (110*10-1000)/1000 *100% = 10% 4. cost: 220*(1-10%) = 198* (1+5%) = 207.9 So, 220-207.9 = 12.1 5. (15600-15000)*2/15000*100% = 8% 6. 4650*6.5%*2+4650*6.5%*1/2+4650 = 5405.625|||||420010%2108%4000 2009-01-18 21:18:37 補充： 1. 6+x=(46+x)/5 30+5x=46+x x=4 2. x*(1+6%)=212 x=200 3. profit % = [(12-2)*110-1000]/1000*100% = 10% 4. new price = 220/(1+10%)*(1+5%) = 210 5. 15000+15000*x/2=15600 x=0.08 x=8% 6. x+x*2.5*6.5%=4650 x(1+2.5*6.5%)=4650 x=4000
有d數學問題唔識~(急!!!)
發問:
1.Pitt is 6 years old and his father is 46 years old now. After how many years will Pitt's age be 1 over 5 of his father's age?2.The cost of a desk is changed by +6% and it becomes $212 after the change. Find the original cost of the desk.3.Joe bought 12 footballs for $1000. If 2 footballs were lost... 顯示更多 1.Pitt is 6 years old and his father is 46 years old now. After how many years will Pitt's age be 1 over 5 of his father's age? 2.The cost of a desk is changed by +6% and it becomes $212 after the change. Find the original cost of the desk. 3.Joe bought 12 footballs for $1000. If 2 footballs were lost and he sold the remaining footballs at $110 each.What was the overall profit per cent? 4.If a shopkeeper sells a shirt at $220,then the profit per cent is 10%.What will be the shopkeeperreduces her profit per cent to 5%? 5.Lancy depoits $15000 in a bank gor 6 months. The bank pays simple interest at a certain interest rate. If Lancy will get the amount of $15600 at the end of the period,what is the interest rate per year? 6.Find the principal that will amount to $4650 after 2.5 years if simple interest is calculated at an interest rate of 6.5% p.a. 更新: 請列明成條橫式,,thZ=]
最佳解答:
1. Let x be the number of years later that Pitt's age will be 1 over 5 of his father's age (6+x)/(46+x) = 1/5 5(6+x) = 46+x 30+5x = 46+x 4x = 16 x = 4 So, after 4 years Pitt's age will be 1 over 5 of his father's age. 2. Let $x be the original cost of the desk x*(1+6%) = 212 1.06x = 212 x = 200 The original cost of the desk is $200. 3. Cost = $1000 Revenue = $110*(12-2) = $1100 Profit percentage = ($1100-$1000)/$1000*100% = 10% 4. cost = $220/(1+10%) = $200 new selling price = $200*(1+5%) = $210 new profit = $210-$200 = $10 5. interest = $15600-$15000 = $600 principal*interest rate(per annual)*time(in year) = interest Let r be the interest rate 15000*r*(6/12) = 600 r = 0.08 (or 8%) The interest rate is 8%. 6. Let $P be the principal P*0.065*2.5 = 4650-P P*(1+0.065*2.5) = 4650 1.1625P = 4650 P = 4000 The principal is $4000.
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其他解答:2. 212*(1-6%) = 199.28 3. (110*10-1000)/1000 *100% = 10% 4. cost: 220*(1-10%) = 198* (1+5%) = 207.9 So, 220-207.9 = 12.1 5. (15600-15000)*2/15000*100% = 8% 6. 4650*6.5%*2+4650*6.5%*1/2+4650 = 5405.625|||||420010%2108%4000 2009-01-18 21:18:37 補充： 1. 6+x=(46+x)/5 30+5x=46+x x=4 2. x*(1+6%)=212 x=200 3. profit % = [(12-2)*110-1000]/1000*100% = 10% 4. new price = 220/(1+10%)*(1+5%) = 210 5. 15000+15000*x/2=15600 x=0.08 x=8% 6. x+x*2.5*6.5%=4650 x(1+2.5*6.5%)=4650 x=4000
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