Answer:
18m
Step-by-step explanation:
Since the given traingles are similar
We get
[tex] \frac{JK}{MN} = \frac{KL}{ML} [/tex]
[tex] \frac{JK}{42} = \frac{21}{49} [/tex]
[tex]JK = \frac{21 \times 42}{49} [/tex]
[tex]JK = \frac{3 \times 7 \times 6 \times 7}{7 \times 7} [/tex]
[tex]JK = 3 \times 6 = 18[/tex]
[tex]JK = 18[/tex]
Hence the distance across river is 18m
