Explanation

Let Cost Price = 100  

Marked Price = 100 + 20% = 120  

Discount 15% of 120 = 18, so Selling Price = 120 - 18 = 102  

Gain = 102 - 100 = 2  

Last verified on 12-04-2026

Explanation

• The principal is the original amount of money deposited or borrowed.
• It is the base amount on which interest or profit is calculated.
• This term is commonly used in banking, loans, and investments.
• Without principal, no interest or markup can be calculated.
• It is the starting value in all financial transactions.

Last verified on 12-04-2026

Explanation

LCM of 4 and 10: multiples of 4 = 4, 8, 12, 16, 20... multiples of 10 = 10, 20...

First common multiple = 20 

Last verified on 12-04-2026

Explanation

• Stationary waves are formed due to the reflection of a wave from a rigid boundary.
• The reflected wave travels in the opposite direction and interferes with the incident wave.
• This interference produces nodes (no displacement) and antinodes (maximum displacement).
• Stationary waves do not transfer energy from one place to another.
• They are commonly observed in stretched strings and air columns.

Last verified on 11-04-2026

Explanation

AND Gate Rule:

• Output = 1 (HIGH) only when all inputs are 1 (HIGH)
• Truth condition: A = 1 AND B = 1 → Output = 1

Last verified on 11-04-2026

Explanation

• Refractive index shows how much light bends when entering a medium.
• Glass is a transparent solid with moderate optical density.
• Its refractive index is a standard value used in physics experiments.
• It is greater than water and less than diamond.
• So, the commonly accepted value for glass is around 1.5.

Last verified on 12-04-2026

Explanation

• Every element is identified by the number of protons in its nucleus.
• This number determines the identity of the element.
• It is written as Z in chemistry.
• It is always equal to the number of electrons in a neutral atom.
• This is called the atomic number.

Last verified on 12-04-2026

Explanation

• Radioactive substances decay over time in a predictable pattern.
• The time required for half of the radioactive nuclei to decay is a standard measure.
• It is used to compare stability of different radioactive elements.
• This concept is widely used in nuclear physics and medicine.
• It is called the half-life of a substance.

Last verified on 12-04-2026

Explanation

• A simple microscope is used to magnify small objects.
• It works by bending light to produce a larger image.
• Only a converging lens can produce a magnified virtual image.
• A convex lens has this property.
• Therefore, simple microscopes use a convex lens.

Last verified on 12-04-2026

Explanation

• When pressure is constant, the volume of a gas changes directly with temperature (in Kelvin).
• As temperature increases, gas particles move faster and occupy more space.
• This relationship is used to describe gas expansion.
• It applies only at constant pressure conditions.
• This is known as Charles’s Law.

Last verified on 12-04-2026