How much will 20 pencils cost if it costs $3.50 for 100 pencils?

20 pencils * ( 3.5 dollars / 100 pencils) = 70 /100 dollars= 70 cents

To find out how much 20 pencils will cost, we need to calculate the price per pencil and then multiply it by the number of pencils.

Let's start by calculating the price per pencil. If it costs $3.50 for 100 pencils, we can divide the total cost by the number of pencils to find the price of one pencil:

Price per pencil = Total cost / Number of pencils

In this case, the total cost is $3.50 and the number of pencils is 100. So, the price per pencil will be:

Price per pencil = $3.50 / 100 = $0.035

Now that we know the price per pencil, we can find the cost of 20 pencils by multiplying the price per pencil by the number of pencils:

Cost of 20 pencils = Price per pencil * Number of pencils

Plugging in the values:

Cost of 20 pencils = $0.035 * 20 = $0.70

Therefore, 20 pencils will cost $0.70.