A six-digit number 7A34B4 is divisible by 36. If B is a prime number, find the value of A.

• 9

• 7

• 5

• 3

Answer explanation

If 7A34B4 is divisible by 36, it must be divisible by 4. By divisibility rule, B4 must be divisible by 4. Since B is prime, B = 2.

If 7A34B4 is divisible by 36, it must be divisible by 9. By divisibility rule, 7+A+3+4+2+4, or 20+A must be divisible by 9.

Since A is a one-digit number, A = 7.

How many triangles are there in the diagram?

30

26

59

60

• 30

• 26

• 59

• 39

Answer explanation

In the sun, helium is produced from hydrogen by:

a) radioactive decay

b) disintegration

c) fission

d) fusion

• radioactive decay

• disintegration

• fission

• fusion

Answer explanation

Explanation: To form helium, two atoms of hydrogen must combine in a process known as nuclear fusion.

Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is___________

• 1:1

• 2:1

• 4:1

• 1:2

Answer explanation

Water undergoes decomposition during electrolysis and forms hydrogen and oxygen gas in the ratio 2:1 by volume. The reaction occurs as follows:

2H2O→2H2+O2

Which chamber of the heart has the most muscular wall?

• right atrium

• left atrium

• left ventricle

• right ventricle

Answer explanation

Left ventricle which has to pump blood into the largest network of blood vessels and has to pumps blood against greater resistance than any other chambers of the heart. Hence, the left ventricle has the thickest muscular wall.

Which process depends on energy from respiration?

• diffusion

• Presistalsis

• Osmosis

• Photosynthesis

Answer explanation

Energy from respiration (ATP) needed for muscle contraction -> peristalsis happens due to muscles contraction on the alimentary canal; ATP for photosynthesis is coming from it self.

What makes nuclear fall-out dangerous to living organisms?

• It causes flooding.

• It damages DNA.

• It causes global warning.

• It damages the soil.

Answer explanation

As radioactive material decays, or breaks down, the energy released into the environment has two ways of harming a body that is exposed to it, Higley said. It can directly kill cells, or it can cause mutations to DNA. If those mutations are not repaired, the cell may turn cancerous.

A chromosome was analysed and found to have 6125 pairs of bases. The type of each base was identified and 2345 of the bases were G. How many of the bases in this chromosome are T?

• 1435

• 3780

• 6185

• 7560

Answer explanation

6125 pairs of bases meant 12250 bases.

Guanine always in pair with Cytosine so their number are the same (2345 assume as pairs since G in pair with C)

While A denine and Thymine must be in pair.

So 6125 pairs - 2345 pairs = 3780 is T as well as the same number with A

Or

12250 - (2 x 2345)* = 7560 (A and T) so T is 7560:2 = 3780

* since number of G = C

Which process occurs during transpiration?

• movement of water vapour through the stomata by diffusion

• evaporation of water from the xylem

• loss of water by osmosis from the guard cells

• movement of water vapour through the spongy mesophyll by active transport

Answer explanation

Transpiration is a process that involves loss of water vapour through the stomata of plants. The loss of water vapour from the plant cools the plant down when the weather is very hot, and water from the stem and roots moves upwards or is 'pulled' into the leaves.

In 12 years, Janice will be 8 times as old as she was 2 years ago. How old is Janice now?

• 4

• 8

• 10

• 2

Answer explanation