Explanation

Given:

• Train length = 90 m
• Tunnel length = 231 m
• Time = 11 seconds

Distance covered = 90 + 231 = 321 m

Speed = Distance ÷ Time
= 321 ÷ 11 = 29.18 m/s

Convert to km/h:

29.18 × 18/5 = 105.05 km/h

Explanation

1. Current Ages:

   • Let Zoya’s current age be $x$
   • Then, Zaid’s current age is $6x$ (since he is six times as old as Zoya).

2. The sum of Ages in 7 Years:

   • In 7 years, Zoya's age will be $x + 7$ and Zaid's age will be $6x + 7$.
   • The sum of their ages in 7 years will be $(x+7)+(6x+7)=49$.

Step 1: Formulate the Equation

x+7+6x+7=49
$$7x+14=49$$

Step 2: Solve for $x$

Subtract 14 from both sides:

$$7x=35$$

Now divide by 7:

$$x=5$$

So, Zoya’s current age is $5$ years and Zaid’s current age is:

$$6x=6\times 5=30$$

Step 3: Determine Zaid’s Age When Zoya Was Born

When Zoya was born, Zaid would have been:

$$30-5=25$$

Explanation

Let daughter age = x

Father age = 5 times daughter age = 5x

Sum of ages = 50

x + 5x = 50

6x = 50

x = 50 / 6 = 8.33

So daughter = 8.33 years

Father = 5 x 8.33 = 41.67 years

Last verified on 02-09-2026

Explanation

Use the set formula: 

Students who study CS or Math = CS + Math - Both  

= 55 + 50 - 10  

= 95 students

Students who study neither = Total students - Students who study CS or Math  

= 100 - 95  

= 5 students

Last verified on 02-09-2026

Explanation

Father’s current age = 72 − 6 = 66 years.

Son’s current age = 66 ÷ 6 = 11 years.

Last verified on 02-09-2026