Question

A nurse mixes 50 cc of a 60% saline solution with a 20% saline solution to produce a 28% saline solution. How much of the 20% solution should he use?

Answer 1

• 200 cc

Explanation:

Let x be the added 20% solution.

The salt content is same:

• 50*0.6 + x*0.2 = 0.28*(x + 50)
• 30 + 0.2x = 0.28x + 14
• 0.28x - 0.2x = 30 - 14
• 0.08x = 16
• x = 16/0.08
• x = 200

Answer 2

Let added amount be y .

• The salt remains same

`\\ \tt\Rrightarrow 50(0.6)+0.2y=0.28(y+50)`

`\\ \tt\Rrightarrow 0.2y+30=0.28y+14`

`\\ \tt\Rrightarrow 0.2y-0.28y=14-30`

`\\ \tt\Rrightarrow -0.08y=-16`

`\\ \tt\Rrightarrow 0.08y=16`

`\\ \tt\Rrightarrow y=(16)/(0.08)`

`\\ \tt\Rrightarrow y=200`