Giải Bài 4 trang 39 SGK Toán 5

Lời giải

Nhận xét: Hai đơn vị thể tích liền nhau hơn (kém) nhau 1000 lần.

Ta có: $1 \text{ m}^3 = 1000 \text{ dm}^3$ ; $1 \text{ dm}^3 = 1000 \text{ cm}^3$ ; $1 \text{ m}^3 = 1\,000\,000 \text{ cm}^3$.

a)

$5 \text{ m}^3 = ? \text{ dm}^3$

Vì $1 \text{ m}^3 = 1000 \text{ dm}^3$ nên:

$5 \text{ m}^3 = 5 \times 1000 = 5000 \text{ dm}^3$

$480 \text{ dm}^3 = ? \text{ m}^3$

Vì $1 \text{ dm}^3 = \dfrac{1}{1000} \text{ m}^3$ nên:

$480 \text{ dm}^3 = 480 : 1000 = 0,48 \text{ m}^3$

b)

$0,25 \text{ m}^3 = ? \text{ cm}^3$

Vì $1 \text{ m}^3 = 1\,000\,000 \text{ cm}^3$ nên:

$0,25 \text{ m}^3 = 0,25 \times 1\,000\,000 = 250\,000 \text{ cm}^3$

$5\,000 \text{ cm}^3 = ? \text{ m}^3$

Vì $1 \text{ cm}^3 = \dfrac{1}{1\,000\,000} \text{ m}^3$ nên:

$5\,000 \text{ cm}^3 = 5\,000 : 1\,000\,000 = 0,005 \text{ m}^3$

c)

$1,9 \text{ dm}^3 = ? \text{ cm}^3$

Vì $1 \text{ dm}^3 = 1000 \text{ cm}^3$ nên:

$1,9 \text{ dm}^3 = 1,9 \times 1000 = 1900 \text{ cm}^3$

$2\,650 \text{ cm}^3 = ? \text{ dm}^3$

Vì $1 \text{ cm}^3 = \dfrac{1}{1000} \text{ dm}^3$ nên:

$2\,650 \text{ cm}^3 = 2\,650 : 1000 = 2,65 \text{ dm}^3$

Đáp số