Estimate the differences. Round the numbers before you subtract. Check your work using the answer key at the end of the exercise.

Examples:

[latex]\begin{array}[t]{rrrrr}&9\,963&\approx&&10\,000 \\-&7\,099&\approx&-&7\,000 \\ \hline &&&&3\,000 \end{array} \ \begin{array}[t]{rrrrr}&70\,534&\approx&&71\,000 \\-&7\,689&\approx&-&8\,000 \\ \hline &&&&63\,000 \end{array}[/latex]

1. [latex]\begin{array}[t]{rr}&687\\-&438\\ \hline \\ \end{array}[/latex]
2. [latex]\begin{array}[t]{rr}&754\\-&236\\ \hline \\ \end{array}[/latex]
3. [latex]\begin{array}[t]{rr}&8\,442\\-& 1\, 876\\ \hline \\ \end{array}[/latex]
4. [latex]\begin{array}[t]{rr}&5 \,630\\-& 1 \,752\\ \hline \\ \end{array}[/latex]
5. [latex]\begin{array}[t]{rr}&5 \,342\\-& 3 \,647\\ \hline \\ \end{array}[/latex]
6. [latex]\begin{array}[t]{rr}&7 \,111\\-& 5 \,982\\ \hline \\ \end{array}[/latex]
7. [latex]\begin{array}[t]{rr}&6 \,031 \\-& 2\, 899\\ \hline \\ \end{array}[/latex]
8. [latex]\begin{array}[t]{rr}&41 \,573\\-& 4\, 846\\ \hline \\ \end{array}[/latex]
9. [latex]\begin{array}[t]{rr}&36 \,154\\-& 9 \,038\\ \hline \\ \end{array}[/latex]
10. [latex]\begin{array}[t]{rr}&46 \,124 \\-& 9 \,762\\ \hline \\ \end{array}[/latex]
11. [latex]\begin{array}[t]{rr}&54 \,751 \\-& 7 \,896\\ \hline \\ \end{array}[/latex]
12. [latex]\begin{array}[t]{rr}&72 \,450 \\-& 31\, 924\\ \hline \\ \end{array}[/latex]
13. [latex]\begin{array}[t]{rr}&81 \,692 \\-& 53\, 908\\ \hline \\ \end{array}[/latex]
14. [latex]\begin{array}[t]{rr}&92 \,163 \\-& 45\, 517\\ \hline \\ \end{array}[/latex]
15. [latex]\begin{array}[t]{rr}&171 \,234\\-& 82\, 169\\ \hline \\ \end{array}[/latex]
16. [latex]\begin{array}[t]{rr}&102 \,085 \\-& 36 \,526\\ \hline \\ \end{array}[/latex]

Exercise 1 Answers

1. [latex]700 - 400 = 300[/latex]
2. [latex]800 - 200 = 600[/latex]
3. [latex]8\,000  - 2\,000  = 6\,000[/latex]
4. [latex]6\,000  - 2\,000  = 4\,000[/latex]
5. [latex]5\,000  - 4\,000  = 1\,000[/latex]
6. [latex]7\,000  -  6\,000  =  1\,000[/latex]
7. [latex]6\,000 - 3\,000 = 3\,000[/latex]
8. [latex]42\,000 - 5\,000 = 37\,000[/latex]
9. [latex]36\,000 - 9\,000 = 27\,000[/latex]
10. [latex]46\,000 - 10\,000  = 36\,000[/latex]
11. [latex]55\,000  -  8\,000  =  47\,000[/latex]
12. [latex]70\,000 -  30\,000  =  40\,000[/latex]
13. [latex]80\,000  -  50\,000  = 30\,000[/latex]
14. [latex]90\,000 -  50\,000  =  40\,000[/latex]
15. [latex]170\,000 - 80\,000 = 90\,000[/latex]
16. [latex]100\,000 - 40\,000 = 60\,000[/latex]

Estimate the following answers. Be sure to round to the largest place value possible before adding or subtracting. Remember to circle the information and underline what is being asked.

Example: On a recent petition about sales tax, Mulan had 2865
people sign. Arnav had 1564 people sign the petition. Estimate how many more people Mulan had sign the petition than Arnav.

On a recent petition about sales tax, Mulan had 2865
people sign. Arnav had 1564 people sign the petition. Estimate how many more people Mulan had sign the petition than Arnav.

[latex]\begin{array}[t]{rrrrr}&2\,865&\text{Estimate: }&&3\,000\\ − &1\,564&&-&2\,000\\ \hline &&&&1\,000\end{array}[/latex]

Mulan had 1000 more people sign the petition.
 

1. On Tuesday, a coffee shop had sales of $8523. On Wednesday, the same coffee shop had sales of $6914. Estimate the difference between Tuesday’s sales and Wednesday’s sales.
2. Last week, 4931 passengers used the ABE Taxi Company. This week, there were 3491 passengers. Estimate how many more passengers used ABE Taxi Company last week.
3. In Japan, people chew 52700 tons of gum. In Russia, people chew 25700 tons of gum. Estimate how many more tons of gum the Japanese chew.
4. In Colombia, there are 1897 bird species. In China, there are 1319 bird species. Estimate how many more bird species there are in Colombia.
5. The whale shark weighs 3500 kilograms. The basking shark weighs 9258 kilograms. Estimate how much more the whale shark weighs.
6. In India, there were 155204 post offices in 2007. In China, there were 59886 post offices. Estimate the difference.
7. By 2008, the Montreal Canadiens had played the most games at 5792. The Buffalo Sabres had played 2952. Estimate how many more games the Montreal Canadiens had played.
8. In 2006, the population of Kelowna was 162276. The population of Prince George was 83225. Estimate how many more people live in Kelowna in 2006.

Exercise 2 Answers

1. [latex]$9\,000 - $7\,000 = $2\,000[/latex]
2. [latex]5\,000 - 3\,000 = 2\,000 \text{ passengers}[/latex]
3. [latex]50\,000 - 30\,000 = 20\,000 \text{ tons}[/latex]
4. [latex]2\,000 - 1\,000 = 1\,000 \text{ species}[/latex]
5. [latex]31\,000 - 9\,000 = 22\,000 \text{ kilograms}[/latex]
6. [latex]160\,000 - 60\,000 = 100\,000 \text{ post offices}[/latex]
7. [latex]6\,000 - 3\,000 = 3\,000 \text{ games}[/latex]
8. [latex]160\,000 - 80\,000 = 80\,000 \text{ people}[/latex]