Questions

Sound is a mechanical vibration and needs a medium for propagation. The higher the density of the medium, the faster the sound travels. So, sound cannot travel through vacuum.

As the sound travels faster in solids than liquids and gases, sound travels faster in the glass than Air and water.

Alum is a common alum, potassium aluminum sulphate K2SO4.Al2SO43.24H2O which makes colloidally suspended impurities in water such as clay to settle down.

Savannas are home to a wide diversity of animals.

Many animals of the savanna migrate throughout the year, searching for food and water. Many of the droughts are seasonal and hit one area before another, so animals are constantly following the rains.

Hence, Rain fall is what often governs animal migration on savannas.

Let length and breadth of rectangle be L cm
and B cm respectively So, ATQ
Area1= (L-6)×B
But this is square, so L-6=B
Area1= (L-6) × (L-6)
Case 2, Area2= L × (B+6),
L=B+6
So, Area2= L × L,
Given, Area2-Area1= 252(L)2-(L-6)2=252
Solving this, L= 24
B= 18
Perimeter= 2(L+B)= 2(24+18)= 84 cm