Geophysics for GATE

Aptitude 2)If  pq = 28 where p and q (p > q) are whole numbers then which of the following can be (p 2  – q 2 )?  a)32  b)83  c)783  d)63 Ans.    p and q can be written in the pairs of (28,1) or (7,4) or (14,2) We have 14 2  – 2 2  = 196 – 4 = 192        Also, 7 2  – 4 2  = 49 – 16 = 33        Also, 28 2  – 1 2  = 784 – 1 = 783        Hence,   p 2  – q 2  = 783

Aptitude     1) A person has to make 146 pieces of a long bar. He takes 4 seconds to cut a piece. What is the total time taken by him in seconds to make 146 pieces?  a)584  b)580  c)730  d)725 Ans .  To make 146 pieces there are 145 cuts required         Each cut takes 4 seconds.        Hence the person will require 145 × 4 = 580 seconds.

GATE 2020 1. )Skin depths in homogeneous media of resistivity  ρ 1  and  ρ 2  are 100 m and 200 m respectively at 1000Hz frequency. The ratio of  ρ 1 / ρ 2  will be...... Ans . Since skin depths are given as 100m and 200 m respectively           so using the  formula,                           skin depth (d) =503  √(ρ/f) , where  ρ- resistivity                                                                                            f- frequency        d1=503 √(ρ1/1000)        d2=503 √(ρ2/1000)                    n...