Question

A girl found that the sum of 673, 32186, 7985 and another number is 61321. What is the missing number?
This should be ONLY SOLVED BY USING ADDITION OR SUBTRACTION OR BOTH.

Answer 1

Step-by-step explanation:

Let, the speed of the stream be x km/hr

Speed of boat in still water =20 km/hr

∴Speed of boat with downstream 20+x km/hr

∴ Speed of boat with upstream 20−x km/hr

As per given condition

20−x

48

−

20+x

48

=1

⟹48[

20−x

1

−

20+x

1

]=1

⟹[

(20−x)(20+x)

20+x−20+x

]=

48

1

⟹

400−x

2

2x

=

48

1

⟹96x=400−x

2

⟹x

2

+96x−400=0

⟹x

2

+100x−4x−400

⟹x(x+100)−4(x+100)=0

⟹(x−4)(x+100)=0

Either, x=4 or x=−100

∵ Speed cannot be negative ∴x=4 km/hr is considered.

∴ the speed of the stream =4 km/hr

verified_toppr

Answer 2

Answer:

the missing number is 8957