An ice cream truck is making its way down the street and two

Solution

Speed of child 1 is v \' = 4m/s

Apperent frequency f \' = 449 Hz

Speed of the sound V = 340 m/s

We know f \' = [(V+v \')/(V-v )]f

            449 = [(340+4) /(340-v ) ] f

             449 = [344/(340-v)]f          ------------( 1)

Speed of child 2 is v \" = 8 m/s

Apperent frequency f \" = 426 Hz

We know f \' = [(V-v \')/(V-v )]f

            426 = [(340-8) /(340+v ) ] f

                  = [336/(340+v)] f         ------------( 2)

Equation( 1) / equation( 2) ==>

449 / 426 = [344/(340-v)][(340+v)/336]

              = (344/336)(340-v)/(340+v)

(449x336)/(426x344) = (340-v)/(340+v)

1.02947 = (340-v) /(340+v)

1.02947 (340+v) = 340-v

350 +1.02947 v = 340 -v

          2.02947 v = -10

                      v = -4.927 m/s

So, speed of the source v = 4.927 m/s

Substitute this in equation( 1) you get ,

449 = [344/(340-4.927)]f

       = 1.0266 f

from this freuqnecy of the source f = 449 / 1.0266

                                                  = 437.34 Hz