Present age of son is 15 years & Present age of A is 45 years.
Let, 5 years ago the age of son was x year
5 years ago the age of A was 4:: year
Present age of son = (x + 5) years
Present age of A = (4x + 5) years
According to the question,
2(x+5+15)=4x+5+15
2x + 40 = 4x + 20
2x = 20
x = 10
Present age of son = (10 + 5) or 1’5 years
Present age of A = (4 x 10 + 5) or 45 years
TK 2800
Let, Present salary of Janaki is Tk. x
She spends for her son’s education after increment
x x 20% + $\frac{170}{2}$
=0.2x + 85
According to the question,
0.2x + 85 = 645
0.2x = 645 — 85
0.22x= 560
x = $\frac{270×10}{2}$= 2800
6.45 km/hr
The motor boat is running upstream at speed of 2 km 1′ hr.
Let, speed of the motor boat in still water is x km / hr.
Speed of the boat in upstream = (x — 2) km / hr
Speed of the boat in downstream = (x + x — 2) or (2x — 2) km / hr
In upstream,
Boat goes 2 km in = 1 hour
Boat goes 10 km in = $\frac{10}{2}$= 5 hour
In downstream,
Boat goes (2x— 2) km in 1 hour
Boat goes 10 km in $\frac{10}{2x-2}$ hour
According to the question,
$\frac{10}{2x-2}$= $\frac{55}{60}$
110x — l 10 = 600
110x = 710
x = 6.45
Question 4:
28 m
In 1000 revolutions the wheel cover = 88 km
In 1 revolutions the wheel cover = $\frac{88}{1000}$ = $\frac{88×1000}{1000}$88 m
Let, diameter of the wheel is 2m
Circumference = 2πr = 88
= 2r = $\frac{88}{π}$
The diameter of the wheel = $\frac{88}{π}$ meter
= $\frac{88}{\frac{22}{7}}$ = 28 meter
Question 5:
$\frac{1}{2}$
Given, 2x= 4y = 8z or x= 2y = 4z
$\frac{1}{2x} + \frac{1}{4y} + \frac{1}{4z} = 4$,
=> $\frac{1}{2x} + \frac{1}{2x} + \frac{1}{x} = 4$
=> $\frac{1}{2x} (\frac{1}{2} + \frac{1}{2} + 1)= 4$
=> x = $\frac{1}{2}$
