Mary is going to have an outdoor party in 10 days. She wants to have her backyard pond covered in water lilies before the party, so she goes to the nursery to buy some water lilies. Mary gives the clerk the dimensions of her pond, and the clerk, knowing the growth rate of the water lilies that he stocks, calculates that if she purchases a single water lily, it will produce a population of ten thousand lilies that will completely cover the surface of the pond in 20 days. Mary reasons that if she buys two water lilies instead of one, she can meet her goal of having the pond surface covered in 10 days. Is there anything wrong with Mary's reasoning? How many water lilies will Mary need to buy to meet her goal?

a. There is nothing wrong with Mary's reasoning b. 2 water lilies.

Step-by-step explanation:

a. This is because, she reasons that if she doubles the amount of water lilies she buys, it would take half the time it takes to produce 10,000 lilies. So, there is nothing wrong with Mary's reasoning.

b. Since it takes 1 water lily to produce 10000 lilies in 20 days, 1 water lily will produce x lilies in 10 days.

So, x = 10000 × 10/20 = 5000 lilies

So, 1 water lily produces 5000 lilies in 10 days.

So, x water lilies will produces 10000 lilies in 10 days.

So x = 10000 × 1/5000 = 2 water lilies

So, 2 water lilies will produce 10000 lilies in 10 days.

So, Mary needs 2 water lilies so she can meet her goal of having the pond surface covered in 10 days.