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**Unformatted text preview: **Now we have two equations in two unknowns x + y = 150 .18x + .78y = 75 I would solve this by elimination x + y = 150 .18x + .78y = 75 multiply by 100 to clear the decimals x + y = 150 18x + 78y = 7500 Multiply the top equation by -18 to clear the x column: (I picked 18 because it’s smaller than 78 - the numbers will be easier to work with) x + y = 150 18x + 78y = 7500 -18x - 18y = -2700 18x + 78y = 7500 Now just add the equations together. The x’s will add up to zero and disappear! 60y = 4800 y = 80 She needs 80ml of 78% solution. Now let’s find the amount of 18% solution and check our work x + y = 150 y = 80 x + 80 = 150 x = 70 Now we have 80 mL of 78% solution and 70 mL of 18% solution. Does this fit our story? Does 80 at 78% + 70 at 18% = 75? 80(.78) + 70(.18) 62.4+ 12.6 = 75 We have a winner! 80 ml of 78% solution and 70 mL of 18% solution...

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- Spring '11
- filer
- Chemistry, Harshad number