Given that Angelo's kayak travels 10km/h in still water, and the river's current flows at a rate of 4km/h.
Travelling downstream means Angelo is travelling with the current, that is the current of the water will add to Angelo's speed.
Their combined speed will be;
![\begin{gathered} v=10\text{ km/h + 4 km/h} \\ v=\text{ 14 km/h} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/vm4w7y9g67wmecvo9see4v5ywx1fmvmbbf.png)
To travel 35 km downstream;
![\text{distance = 35km}](https://img.qammunity.org/2023/formulas/mathematics/college/9daoak8sfuasaexuiwhgmmply6hghurjqq.png)
Recall that;
![\begin{gathered} \text{speed = }\frac{\text{ distance}}{\text{time}} \\ \text{time = }\frac{\text{ distance}}{\text{ speed}} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/k9p6s5aaxgap7sofmo8vmwk8xgqfcgnhor.png)
substituting the given values;
![\begin{gathered} \text{time = }\frac{35\operatorname{km}}{14\text{ km/h}} \\ \text{time =2.5 hours} \end{gathered}]()
Therefore, it'll take 2.5 hours
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