GoalReview bar graphs, dot plots, place value and length from the first weeks of the term.
New words
bar graph · a graph that uses bars to show how many are in each groupdot plot · a graph that shows data as dots above a number lineplace value · what a digit is worth because of its place in a numbermillimetre (mm) · a very small unit of length; 10 mm = 1 cm
Explanation
In this review we visit graphs, big numbers and length. A bar graph shows how many are in each group, and we read the height of each bar. A dot plot has a title, a labelled number line with its unit, a key and exactly one dot for each piece of data. In a number like 48,306, each digit has a value that depends on its place: 4 ten thousands, 8 thousands, 3 hundreds, 0 tens and 6 ones. In expanded form it is 40,000 + 8,000 + 300 + 6. To measure length we choose the unit that fits: mm for tiny things, cm for a pencil and m for a room. Remember that 10 mm = 1 cm and 100 cm = 1 m.
Worked examples
Use the bar graph above. Omar read 9 books and Mina read 4, so Omar read 9 − 4 = 5 more. All five children read 6 + 9 + 4 + 8 + 5 = 32 books.
The dot plot shows the lengths of 11 leaves. The most common length is 7 cm, with 4 dots. The leaves longer than 7 cm are 2 + 1 = 3 leaves. The dots add up: 1 + 3 + 4 + 2 + 1 = 11.
Hundred thousands
Ten thousands
Thousands
Hundreds
Tens
Ones
5
0
7
2
1
4
Place value: 507,214 has 5 hundred thousands, 0 ten thousands, 7 thousands, 2 hundreds, 1 ten and 4 ones. In expanded form it is 500,000 + 7,000 + 200 + 10 + 4. The zero holds the ten thousands place.
Class activity
Class survey. Ask 10 classmates or family members how many brothers and sisters they have. Make a dot plot with a title, a labelled number line and a key. Then write one number with 6 digits and one with 5 digits, write both in expanded form and say which is bigger and why.
Practice
1
Read the length of the line on the ruler.
The line ends at 7, so it is 7 cm long.
2
Order from the smallest to the greatest: 48,306; 84,306; 480,306; 48,036.
48,036; 48,306; 84,306; 480,306. The number with 6 digits is the greatest; among the others compare from the left.
3
Write 62,509 in expanded form.
60,000 + 2,000 + 500 + 9.
4
Choose mm, cm or m: the height of a door, the length of an eraser, the width of an ant.
A door: m. An eraser: cm. An ant: mm.
5
Use the bar graph in this lesson. How many more books did Omar read than Karim?
Omar read 9 and Karim read 5. 9 − 5 = 4 more books.
