Let y be the number of gallons of 60% solution. Let x be the number of gallons of 30% solution. The final solution, then, is to have 9 gallons of pure alcohol. "18 gallons of 50% solution" means: 50%, or half, is pure alcohol. How many gallons of 30% alcohol solution and how many of 60% alcohol solution must be mixed to produce 18 gallons of 50% solution? That solution contains 9 gallons of pure alcohol. Means: 25%, or one quarter, of the solution is pure alcohol. Multiply equation 1) by −10 and equation 2) by 100: 1')
To see the answer, pass your mouse from left to right Samantha has 30 coins, consisting of quarters and dimes, which total $5.70. These are the simultaneous equations to solve. (To change a percent to a decimal, see Skill in Arithmetic, Lesson 4.)Īgain, in equation 2) let us make the coefficients whole numbers by multiplying both sides of the equation by 100: 1)
The total interest on the investment was $2,100. invested $30,000 part at 5%, and part at 8%. To cover the answer again, click "Refresh" ("Reload").Įxample 3. To see the answer, pass your mouse over the colored area. Those simultaneous equations are solved in the usual way. We call the second equation 2' ("2 prime") to show that we obtained it from equation 2). In equation 2), we will make the coefficients into whole numbers by multiplying both sides of the equation by 10: 1) And again we must get two equations out of the given information. Let y be the number of children's tickets.Īgain, we have let x and y answer the question. Adult tickets cost $8.50, children's cost $4.50, and a total of $7300 was collected. Therefore, according to the exression for x, Andre hasĮxample 2. and substitute it into equation 2): y + 40 + 22īob has $106. In this example, we can solve equation 1) for x - x − 20 To solve any system of two equations, we must reduce it to one equation in one of the unknowns.
(Andre has twice as much as Bob, on the right - after Bob gives him $22.) "While if Bob gave Andre $22, Andre would then have twice as much (Andre - x - has the same amount as Bob, after he gives him $20.) "If Andre gave Bob $20, they would have the same amount." (In general, to have a unique solution, the number of equations must equal the number of unknowns.) How can we get two equations out of the given information? We must translate each verbal sentence into the language of algebra. Since there are two unknowns, there must be two equations. Let y be the amount that Bob has.Īlways let x and y answer the question - and be perfectly clear about what they represent! Let x be the amount of money that Andre has. While if Bob gave Andre $22, Andre would then have twice as much as Bob. If Andre gave Bob $20, they would have the same amount. H ERE ARE SOME EXAMPLES of problems that lead to simultaneous equations.Įxample 1.