Question

on which two days were 2500 books sold, when rounded to 2 significant figures?

Explanation:

🆕 New Concept Discovered: Significant Figures
Rounding numbers to a specific level of precision

Step 1: Understand significant figures

To round a number to \(2\) significant figures, we look at the first two non-zero digits from the left.

For four-digit numbers like the ones in the table, the first two digits represent the thousands and hundreds places. We round to the nearest hundred by looking at the third digit (the tens place):

• If the tens digit is \(5\) or more, we round up.
• If the tens digit is \(4\) or less, we round down.

We want to find which two numbers round to \(2500\). This means the rounded value must have \(2\) and \(5\) as its first two digits, followed by zeros: \(2500\).

Step 2: Round each day's sales to 2 significant figures

Let's test the values for each day:

• Monday: \(2361\)
• The first two digits are \(23\). The third digit is \(6\) (round up).
• \(2361

ightarrow 2400\)

• Tuesday: \(2580\)
• The first two digits are \(25\). The third digit is \(8\) (round up).
• \(2580

ightarrow 2600\)

• Wednesday: \(2680\)
• The first two digits are \(26\). The third digit is \(8\) (round up).
• \(2680

ightarrow 2700\)

• Thursday: \(2453\)
• The first two digits are \(24\). The third digit is \(5\) (round up).
• \(2453

ightarrow 2500\) (Match!)

• Friday: \(2553\)
• The first two digits are \(25\). The third digit is \(5\) (round up).
• \(2553

ightarrow 2600\)

• Saturday: \(2547\)
• The first two digits are \(25\). The third digit is \(4\) (round down).
• \(2547

ightarrow 2500\) (Match!)

• Sunday: \(2446\)
• The first two digits are \(24\). The third digit is \(4\) (round down).
• \(2446

ightarrow 2400\)

Answer:

Thursday and Saturday