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Mathematics Challenge for Grade 8

Authored by Tika Astuti

Mathematics

8th Grade

Mathematics Challenge for Grade 8
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20 questions

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1.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Simplify the expression: 3x + 5x - 2.

8x + 2

5x - 2

3x + 2

8x - 2

Answer explanation

Combine like terms: 3x + 5x = 8x. The constant -2 remains unchanged. Thus, the simplified expression is 8x - 2, which matches the correct answer.

2.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

If the area of a triangle is 24 cm² and the base is 8 cm, what is the height?

4 cm

8 cm

10 cm

6 cm

Answer explanation

To find the height of the triangle, use the formula: Area = 1/2 * base * height. Rearranging gives height = (2 * Area) / base. Substituting the values: height = (2 * 24) / 8 = 6 cm. Thus, the height is 6 cm.

3.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

What is the value of x in the equation: 2(x - 3) = 10?

8

5

10

3

Answer explanation

To solve 2(x - 3) = 10, first divide both sides by 2: x - 3 = 5. Then, add 3 to both sides: x = 8. Thus, the value of x is 8.

4.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Calculate the circumference of a circle with a radius of 7 cm.

50.24 cm

28.00 cm

43.98 cm

21.99 cm

Answer explanation

The circumference of a circle is calculated using the formula C = 2πr. For a radius of 7 cm, C = 2 × π × 7 ≈ 43.98 cm. Thus, the correct answer is 43.98 cm.

5.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

If a bag contains 3 red, 5 blue, and 2 green marbles, what is the probability of picking a blue marble?

0.1

0.25

0.75

0.5

Answer explanation

The total number of marbles is 3 red + 5 blue + 2 green = 10. The probability of picking a blue marble is the number of blue marbles (5) divided by the total (10), which is 5/10 = 0.5.

6.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Find the least common multiple (LCM) of 12 and 15.

30

60

75

45

Answer explanation

To find the LCM of 12 and 15, we can list the multiples: 12 (12, 24, 36, 48, 60...) and 15 (15, 30, 45, 60...). The smallest common multiple is 60, making it the LCM.

7.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

A rectangle has a length of 10 cm and a width of 4 cm. What is its perimeter?

28 cm

30 cm

24 cm

20 cm

Answer explanation

To find the perimeter of a rectangle, use the formula P = 2(length + width). Here, P = 2(10 cm + 4 cm) = 2(14 cm) = 28 cm. Thus, the correct answer is 28 cm.

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