Question

a boat takes 30 minto go 10 km upstream 20 min to go 10 km come bake down stream . find the speed of the current

Answer 1

$\color {red}\huge\bold\star\underline\mathcal{Question:-}$ we have to Find speed of current .

$\huge\underline\blue{\sf Given:}$ to cover 10km upstream he need = 30 min and while coming back downstream he take 20 min ..

$\bold{\boxed{\huge{\boxed{\orange{\small{\boxed{\huge{\red{\bold{\:Answer}}}}}}}}}}$

we now that ,

$\large\red{\boxed{\sf speed={\frac{distance}{Time}}}}$

so,

upstream distance = 10km

upstream time = 30 min = 30/60 = 0.5 hours

Upstream speed = $\huge{\frac{</strong><strong>1</strong><strong>0</strong><strong>}{</strong><strong>0</strong><strong>.</strong><strong>5</strong><strong>}}$ = 20km/h

similarly ,

downstream speed = $\huge{\frac{10}{</strong><strong>1</strong><strong>/</strong><strong>3</strong><strong>}}$ = 30km/h

Now , we know that ,

speed of current = (Downstream speed - upstream speed)/2

so,

speed of current = (30-20)/2 = 5km/h (Ans)