Question

a survey asked a random sample of students if they estimated they spent more or less than an hour a day on social media.

• 12 seventh graders estimated they spent more than an hour.
• 21 eighth graders estimated they spent less than an hour.
• 30 total students estimated they spent more than an hour.
• 51 total students estimated they spent less than an hour.

fill in the missing values in the table below.
social media

Explanation:

Step1: Fill in the total row

• More than an hour total: Given as \(30\).
• Less than an hour total: Given as \(51\).
• Overall total: \(30 + 51=81\).

Step2: Fill in the 7th - grade more than an hour

Given as \(12\).

Step3: Fill in the 8th - grade more than an hour

Since the total for more than an hour is \(30\) and 7th - graders with more than an hour is \(12\), then 8th - graders with more than an hour is \(30−12 = 18\).

Step4: Fill in the 7th - grade less than an hour

Since the total for less than an hour is \(51\) and 8th - graders with less than an hour is \(21\), then 7th - graders with less than an hour is \(51−21=30\).

Step5: Fill in the 7th - grade total

\(12 + 30=42\).

Step6: Fill in the 8th - grade total

\(18+21 = 39\).

Answer:

	More	Less	Total
8th grade	\(18\)	\(21\)	\(39\)
Total	\(30\)	\(51\)	\(81\)