Respuesta :

42÷6=7
10×7=70

10 bags of plaster will cover 70 m.  I hope this helps!
abudi
let the unknown area covered be x

area covered bags
42m 6
x 10
CROSS MULTIPLY :
6X = 42 x 10
x = 420 / 6 = 70 m squared

HOPE IT HELPS !!!