英文数学题 要求列方程解答An investor received $1400 interest per annum from a sum of money, with part of it invested at 10% and the remainder at 7% simple interest.This investor found that if she interchanged the amounts she had invested
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![英文数学题 要求列方程解答An investor received $1400 interest per annum from a sum of money, with part of it invested at 10% and the remainder at 7% simple interest.This investor found that if she interchanged the amounts she had invested](/uploads/image/z/2831423-23-3.jpg?t=%E8%8B%B1%E6%96%87%E6%95%B0%E5%AD%A6%E9%A2%98+%E8%A6%81%E6%B1%82%E5%88%97%E6%96%B9%E7%A8%8B%E8%A7%A3%E7%AD%94An+investor+received+%241400+interest+per+annum+from+a+sum+of+money%2C+with+part+of+it+invested+at+10%25+and+the+remainder+at+7%25+simple+interest.This+investor+found+that+if+she+interchanged+the+amounts+she+had+invested)
英文数学题 要求列方程解答An investor received $1400 interest per annum from a sum of money, with part of it invested at 10% and the remainder at 7% simple interest.This investor found that if she interchanged the amounts she had invested
英文数学题 要求列方程解答
An investor received $1400 interest per annum from a sum of money, with part of it invested at 10% and the remainder at 7% simple interest.This investor found that if she interchanged the amounts she had invested she could increase by $90 per annum.Calculate the total amount invested
英文数学题 要求列方程解答An investor received $1400 interest per annum from a sum of money, with part of it invested at 10% and the remainder at 7% simple interest.This investor found that if she interchanged the amounts she had invested
Let the amounts invested in 10% and 7% x and y dollars respectively:
x*10% + y*7% = 1400
x*7% + y*10% = 1400 + 90
y = 10000
x = 7000
Total is $17000
设为x,invest y
得到0.1y†0.07(x-y)=1400.
0.1(x-y) 0.07y-1400=90
0.07x-0.03y=1400
0.1x-0.03y=2300
0.03x=900
x=30000
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