Final answer:
To find the number of scoops Tommy shoveled, divide the remaining volume of sand by the decrease per scoop. Tommy shoveled 4 scoops of sand.
Step-by-step explanation:
To find the number of scoops Tommy shoveled, we can set up an equation. Let's denote the number of scoops as 'x'. With each scoop, Tommy decreased the pile by 6 cubic feet, so the equation becomes: 6x = 20. To solve for x, we can divide both sides of the equation by 6: x = 20 / 6. Simplifying further, we find that x = 10 / 3, which is approximately equal to 3.33.
Since we can't have a fractional number of scoops, we round up to the nearest whole number. Therefore, Tommy shoveled 4 scoops of sand.