Build a simple invoice line

What you'll build: the total for one invoice line, including tax.

What you need: Nothing but this page.

Why this matters: quantity × price × tax is the core of every invoice and order form.

Step 1 — Quantity times price

3 items at $12.50 each.

=3*12.5 // => 37.5

Step 2 — Add 8% sales tax

=3*12.5*1.08 // => 40.5

What just happened: multiplying by 1.08 adds 8% tax in one step.

Try changing…

• Your own quantity, price, and tax rate.

You learned

• Chain multiplications left to right.
• Multiply by 1 + rate to add a percentage.

Next: Monthly loan payment