Question

The surface area of a cuboid is 1300 cm .if it's length is 15 cm and height is 20 cm find its breadth

Answer 1

Correct question:

The surface area of a cuboid is 1300 cm sq. If it's length is 15 cm and height is 20 cm find its breadth.

SOLUTION:

Given-

• Total surface area of cuboid = 1300cm sq.
• The length (l) of the cuboid = 15cm.
• The height (h) of the cuboid = 20cm.

To be found:

⇒ The breadth(b) of the cuboid.

$\star$ The formula to find the Total surface of the cuboid

= 2(lb + bh + hl) unit sq.

Now,

⇒ 2(lb + bh + hl) = 1300

⇒ (lb + bh + hl) = 1300 ÷ 2

[∵ Taking 2 to RHS ]

⇒ [ (15)(b) + (b)(20) + (20)(15) ] = 650

[ Putting the values of length and height ]

⇒ 15b + 20b + 300 =  650

⇒ 35b + 300 = 650

⇒ 35b = 650 - 300

[ Taking 300 to RHS ]

⇒ 35b = 350

⇒ b = 350 ÷ 35

[Taking 35 to RHS]

⇒ b = 10cm

Hence,

The breadth(b) of the cuboid is 10cm.

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Verification:

2(lb + bh + hl)

= 2[ (15)(10) + (10)(20) + (20)(15) ]

= 2[150 + 200 + 300]

= 2[650]

= 1300 = TSA of the cuboid.

Hence, verified.

Answer 2

Answer:

Breadth of the cuboid = 10 cm

Step-by-step explanation:

Given : Surface area of a cuboid = 1300 cm

Length = 15 cm, Height = 20 cm

Let the breadth of cuboid be x cm

Formula used : Surface area of a cuboid = 2(lb + bh + hl) sq. units

→ 1300 = 2(15 × x + x × 20 + 20 × 15)

→ 650 = 15x + 20x + 300

→ 350 = 35x

→ x = 10