Answer
$78.35^{\circ}$
Work Step by Step
To convert $78^{\circ} 21'$ to decimal degrees, let's break it as-
$78^{\circ} 21'$ = $78^{\circ}$ + $21'$
Now on dividing $21'$ by 60, we have the number of "decimal degrees" equivalent
to $21'$ (as $ 1^{\circ} = 60'$)
Therefore
$78^{\circ} 21'$ = $78^{\circ}$ + $(\frac{21}{60})^{\circ}$
$78^{\circ} 21'$= $78^{\circ}$ + $0.35^{\circ}$
$78^{\circ} 21'$= $78.35^{\circ}$
