I found an answer from www.quora.com

How can we see the Crab Nebula, when it is only 1,001 years old ...

How do astronomers calculate the distance of a star that is **5.74** million light years
... Answered **3** years ago · Author has **1.2**K answers and 545.6K answer views ...
and 1,001 years ago **people** on Earth saw it happening in real time from **our**
frame ... Andre Engels, M.A. **Mathematics** & Physics, University of Groningen (
1996).

For more information, see How can we see the Crab Nebula, when it is only 1,001 years old ...

I found an answer from www.nasa.gov

Space **Math** V

additional challenges in the **math** and physical science curriculum in grades 9 ...
findings and compete for the necessary funding for **their** space craft. ... km/s the
distance is (2500-136)/412 = **5.74** megaparsecs ( or 18,700,000 light ... x (1.737 x
108)3 = 2.2 x 1025 **cm3**, so the **density** = 7.4 x 1025 grams / 2.2 x 1025 **cm3**.

For more information, see Space **Math** V

I found an answer from ncert.nic.in

**Units** & **Measurement**

number (or numerical **measure**) accompanied by a **unit**. Although the ... The base
**units** for **length**, **mass** and time in these systems ... **significant figures** are 2, which
is reliable and ... **PHYSICS**. 26. ◁ **mass density** is obtained by deviding **mass** by
the **volume** of the substance. ... **arithmetic operations** can be understood **from**.

For more information, see **Units** & **Measurement**

**Rounding off the Uncertain Digits**

The preceding digit is left unchanged if the digit to be removed is less than 5

Example: 9.82 is rounded to 9.8.

The preceding digit is increased by one if the digit to be removed is greater than 5.

Example: 6.87 is rounded to 6.9

Read more: https://byjus.com/physics/error-significant-figures-rounding-off/

Given that

Substance mass m = 5.74 g

Volume of substance V = 1.2 cm^3

Formula of Density \rho = \frac{\text{mass}}{\text{volume}}

\rho = \frac{5.74}{1.2}

\rho = 4.78\bar{3}

Rounding to 4 significant digits

\rho = 4.8

Hence, density of the substance \rho = 4.8 g cm^{-3}