A seesaw spinner designed for children aged 6-8 years old has 4 seats. The total weight limit for 4 riders is 170 pounds. 4 children want to use the seesaw spinner. 3 of the 4 children already weigh a total of 120 pounds. At most how heavy can the 4th child weigh for the total weight to be within the limit?
Since the total weight limit for 4 riders is 170 pounds, and 3 of the children already weigh a total of 120 pounds, the remaining weight that the 4th child can weigh is:
170 pounds (total weight limit) - 120 pounds (weight of 3 children) = 50 pounds
Therefore, the 4th child can weigh at most 50 pounds for the total weight to be within the limit.