বিগত সালের প্রশ্ন ও প্রশ্ন ব্যাংক
বিসিএস, ব্যাংক, প্রাথমিক শিক্ষক ও সকল সরকারি চাকরির বিগত সালের প্রশ্ন ও অধ্যায়ভিত্তিক নির্ভুল সমাধান
Solution:
Speed of the swimmer in still water = 4 km/h
Speed of the current = 2 km/h
Distance one way = 12 km
Downstream Speed = 4 + 2 = 6 km/h
Upstream Speed = 4 - 2 = 2 km/h
Time taken downstream = 12/6 = 2 hours
Time taken upstream = 12/2 = 6 hours
Total time = 6 + 2 = 8 hours
Solution:
Speed of athlete = 200 m/24 sec
= (200 × 18)/(5 × 24) = 30 km/hour
Solution:
Let the speed of the man be x km/h
Distance covered by the man in 10 min = Distance covered by the bus in 5 min
According to the question
⇒ x × 10/60 = 30 × 5/60
⇒ 10x = 150
⇒ x = 15 km/h
∴ Speed of the man is 15 km/h
Solution:
Given,
Man covers half of his journey at 12 km/h
The remaining half at 6 km/h
His average speed is = (2 × 12 × 6)/(12 + 6)
= 144/18 = 8 km/h
Solution:
Let, the two–digit number be = (10x + y) where x < y.
Number obtained on reversing the digits = (10y + x)
ATQ,
10y + x = 4 (10x + y) - 24
⇒ 40x + 4y - 10y - x = 24
⇒ 39x - 6y = 24
⇒ 13x - 2y = 8 ....(i)
Again, y - x = 7
y = x + 7 ....(ii)
⇒ 13x - 2 (x + 7) = 8
⇒ 13x - 2x - 14 = 8
⇒ 11x = 14 + 8 = 22
⇒ x = 22/11
∴ x = 2
From equation (ii),
y - 2 = 7
⇒ y = 2 + 7
∴ y = 9
So, Number = 10x + y = (10 × 2) + 9 = 29
Solution:
Suppose, a = 1 and b = 2
a + b = 1 + 2 = 3
ab + 1 = 1 × 2 + 1 = 3
=10
Solution:
Let the original number be x
ATQ,
{5(x + 7)/9} - 3 = 12
⇒ {5(x + 7) - 27}/9 = 12
⇒ 5(x + 7) - 27 = 108
⇒ 5x + 35 - 27 = 108
⇒ 5x + 8 = 108
⇒ 5x = 100
∴ x = 20