We have 16 Oz birdseed. And 10% is sesame seed.

At 10% of 16 Oz we have \(\frac{10}{100}\times 16=1.6\) Oz sesame seeds

Now lets say we add \(x\) oz of sesame seeds more to the mixture.

Total weight of sesame seeds in the new mixture=1.6 +x.

Weight of the mixture= 16+x. (Remember you added extra weight to the total mixture not just the sesame part)


Now the new mixture has to be 20% sesame by weight

\(\frac{1.6+x}{16+x}= 20%= \frac{20}{100}\)

\(\frac{1.6+x}{16+x}=0.2\)
or \(1.6+x= 0.2(16+x)\)
or \(1.6+x= 3.2+0.2x\)
or \(0.8x= 1.6\)

Thus \(x=2\) Oz.




Note