Answer :
Since ΔPRE is similar to POC, then the ratio of the corresponding sides are equal.
Let the distance across the river be x and given that RO is 45m, OC is 90m and RE is 60m, then:
[tex] \frac{x}{60} = \frac{x+45}{90} \\ \\ \Rightarrow90x=60x+2700 \\ \\ \Rightarrow30x=2700 \\ \\ \Rightarrow x=90m[/tex]
Therefore, the distance across the river is 90m.
Let the distance across the river be x and given that RO is 45m, OC is 90m and RE is 60m, then:
[tex] \frac{x}{60} = \frac{x+45}{90} \\ \\ \Rightarrow90x=60x+2700 \\ \\ \Rightarrow30x=2700 \\ \\ \Rightarrow x=90m[/tex]
Therefore, the distance across the river is 90m.