+817 Help I'm really stuck here
Ruth has a beaker containing a solution of 800 mL of acid and 200 mL of water. She thinks the solution is a little strong, so she drains 150 mL from the beaker, adds 150 mL of water, and stirs the solution. Ruth thinks the solution is still too strong, so again she drains 150 mL from the beaker, and adds 150 mL of water. How many mL of water are now in the beaker?
+129771 She starts with 1000ml of solution
Initially the ratio of water to acid is 200 : 800 = 1 : 4
When she pours off 150 ml of solution the first time she now has 850 ml of solution
The ml of water now = 1 /( 1 + 4) *(850) = 1/5 * 750 = 170ml
And the ml of acid = 850 - 170 = 680 ml
Note that the ratio of water to acid is still 170 : 680 = 1 : 4
When she adds 150 ml of water the first time she now has 1000ml again
But now she has 170 + 150 = 320 ml of water (the acid amt hasn't changed)
The new ratio of water to acid is 320 : 680 = 8 : 17
The second time she pours off 150ml the ratio of water to acid has not changed
She now has 850 ml of solution
The ml of water is now 8 / ( 8 + 17) * 850 = 272
The ml of acid is 850 - 272 = 578 ml
Finally ....adding back 150 ml of water gives us 1000 ml again
She now has 272 + 150 = 422 ml of water
And she still has 578 ml of acid
So she ends up with 422 ml of water and 578 ml of acid
The final ratio of water to acid is 422 : 578 = 211 : 289
