Madame Dubois bought 20 pearl necklaces for $500. Becoming bored quickly, she sold 3/4 of them at $40 each. She sold the rest at cost price. How much money did she make?

Find cost of 1 necklace:

20 necklaces = $500

1 necklace = $500 : 20 = $25

Find Sales of 3/4 of the necklaces:

3/4 of 20 = 3/4 x 20 = 15 necklaces

15 necklaces sold at $40 each = 15 x 40 = $600

Find Sales of the remaining necklaces:

20 - 15 = 5

5 necklaces sold at $25 = 5 x 25 = $125

Find profit:

Total Sales = $600 + $ 125 = $ 725

Total profit made = $725 - $500 = $225

Answer: She made $225