A dehydrated patient needs a 6.4% saline IV.Unfortunately the hospital only has bags of 6% and 8% saline solutions.How many liters of each of these solutions should be mixed together to yield 1 liter of the desired concentration?

Answer 1

let x be the amount of 6% saline
so, 1-x = amount of 8% saline

.06x + .08(1-x) = .064*1
.06x + .08 - .08x = .064
.02x = .016
x = .8

so, .8L of 6% and .2L of 8%

note that 6.4% is 1/5 of the way from 6% to 8%, so the 8% volume is 1/5 of the total volume.