You need a 30% alcohol solution. On hand, you have a 780 mL of a 15% alcohol mixture. You also have 90% alcohol mixture. How much of the 90% mixture will you need to add to obtain the desired solution?

You will need mL of the 90% solution?

PLEASE HELP!!! BRAINLIEST! FOR MY FINAL!!!

195 mL of the 90% solution

Step-by-step explanation:

Let the number of mL of 90% mixture = x

Hence, our equation is

780mL × 15% + x mL × 90% = (780mL + x) 30%

117 + 0.9x = 234 + 0.3x

Collect like terms

0.9x - 0.3x = 234 - 117

0.6x = 117

x = 117/0.6

x = 195 mL

Therefore, You will need 195 mL of the 90% solution

angle addition postulate

2x=56

step-by-step explanation: