a boy ate 100 cookies in 5 days. Each day he ate 6 more than the day before. How many cookies did he eat on the first day?

Question

Problem of the day for fourth graders.

Answer 1

I tutor ESL and I have used this problem to work on the language of math.  Some students calculate this word problem in a few seconds. Others never figure it out.  

The answer seems to be that the boy ate 8 cookies on the first day. 

 

On Day 1 he ate 8 cookies.

On Day 2 he ate 6 more than his Day 1 total: 14  (8 + 6)

On Day 3 he ate 6 more than his Day 2 total: 20 (14 + 6)

On Day 4 he ate 6 more than his Day 3 total: 26 (20 + 6)

On Day 5 he ate 6 more than his Day 4 total: 32 (26 + 6)

 

8 + 14 + 20 + 26 + 32 = 100.  This shows that his first day total was 8 cookies. 

 

As an antidote to the math problem, I use this rather silly word problem:

Mary's father has four children. Three are named Leila, Linda, and Luisa. What is the 4th child's name?

 

For unknown reasons, this problem is very hard for many.  

 

 

Answer 2

f = number of cookies on first day

f + 6 = number of cookies on second day

f + 12 = number of cookies on third day

f + 18 = number of cookies on fourth day

f + 24 = number of cookies on the fifth day

 

f + f + 6 + f + 12 + f + 18 + f + 24 = 100

5f + 60 = 100

5f = 40

f = 8

 

He ate eight cookies on the first day.