To find the total surface area of a rectangular block (rectangular prism), we use the formula:

$\text{Total Surface Area} = 2(\text{length} \times \text{width} + \text{width} \times \text{height} + \text{height} \times \text{length})$

Given the dimensions of the block:

• Length ($l$) = 5 cm
• Width ($w$) = 4 cm
• Height ($h$) = 3 cm

Plugging these values into the formula:

$\text{Total Surface Area} = 2(5 \times 4 + 4 \times 3 + 3 \times 5)$

Now, calculate each product:

$5 \times 4 = 20$ $4 \times 3 = 12$ $3 \times 5 = 15$

Add these values:

$20 + 12 + 15 = 47$

Finally, multiply by 2 to get the total surface area:

$\text{Total Surface Area} = 2 \times 47 = 94 \text{ square centimetres}$

Conclusion:

The correct answer is:

b. 94 square centimetre

Would you like further details or have any other questions? Here are some related questions to consider:

1. How would the surface area change if each dimension is doubled?
2. What is the volume of the rectangular block with these dimensions?
3. How do you calculate the surface area of a cube with a side length of 5 cm?
4. What happens to the surface area if one dimension is halved?
5. Can you derive the formula for the surface area of a rectangular prism?

Tip: Remember that the total surface area of a rectangular block is the sum of the areas of all six faces.