Let's find the area of the glass window by itself. To find the area, all you have to do is do lw=a.
I'm going to turn it into a decimal for it to be easier to multiply.
3.5×2.75= 9.625
We have the area, now let's find the area of the colored squares but multiply.
.25×.25= .0625
We should now divide the area of the glass window by the area of the colored squares to find how any were used.
9.625÷.0625=154
The artist used 154 colored squares for his glass window.