We must observe the economy in the use of materials. Give reason.
We must observe the economy in the use of materials because they directly or indirectly affect our environment. Most of the natural materials which we obtain from our environment are exhaustible/non-renewable resources i.e. once these resources are finished they cannot be renewed again or even if they can, it would take several years to do so.
For example, our forests from where we obtain wood are precious resources because once a forest is destroyed, it would take several years to renew that forest.
Also, destroying the forests for our needs affects the habitat of several other species of organisms and plants. The man-made materials which we use are largely non-biodegradable for example plastic etc. Increased use of man-made materials poses a threat to the environment because their disposal is not easy and leads to environmental pollution. These examples state the importance of judicious use of both natural and man-made materials.