Whole numbers to one billion

Advanced Math 5 · Unit 1 · place-value-billion · Teacher edition

place-value-billion

Name ______________________________Date ______________

1.
Round $438{,}516{,}207$ to the nearest million.
Answer: ______________
2.
A roll of ribbon is $3.45$ m long. A factory has $10^3$ rolls. What is the total length of ribbon, in metres?
Answer: ______________
3.
One bead has a mass of $4.2$ grams. What is the mass of $100$ beads, in grams?
1. (A)
  $4.200$
2. (B)
  $42$
3. (C)
  $420$
4. (D)
  $4{,}200$
5. (E)
  $0.042$

Answer key — Whole numbers to one billion

1.
439000000place-value-billion-01
$438{,}516{,}207$ is between $438{,}000{,}000$ and $439{,}000{,}000$ . The hundred-thousands digit is $5$ , so round up: $\mathbf{439{,}000{,}000}$ .
2.
3450place-value-billion-02
$10^3 = 1{,}000$ , and $3.45 \times 1{,}000 = 3{,}450$ : the point moves three places right and a zero fills the empty place. Total length $\mathbf{3{,}450}$ m. ( $3.45000$ is the same number as $3.45$ ; writing zeros after the point changes nothing.)
3.
(C)
$420$
place-value-billion-03
$4.2 \times 100 = 420$ grams. Sense check: $100$ beads of about $4$ g each is about $400$ g. Answer $\mathbf{420}$ . ( $4.200$ is still $4.2$ — zeros after the point add nothing; $42$ moves the point only one place; $4{,}200$ moves it three; $0.042$ divides instead.)