Households with efficient appliances and good maintenance can reduce water consumption by about 35%. If half of the residential consumption in town W in 2010 was by households with efficient appliances and good maintenance, approximately how many gallons of water (in billions) were saved that year?
A. 5
B. 14
C. 40
D. 52
E. 65
Λύση (B):
Residential consumption in 2010 = περίπου 52 δισεκατομμύρια. Παίρνοντας το μισό του ποσού αυτού έχουμε 26 το οποίο αντιπροσωπεύει το νερό που χρησιμοποιήθηκε από τα νοικοκυριά με “efficient appliances and plumbing”.
Έστω W η ποσότητα νερού που θα χρησιμοποιούσαν τα σπίτια αυτά εναλλακτικά.
Άρα έχουμε :
26 = (100% – 35%)* W [katex]\Rightarrow[/katex] W=40
Επομένως τα “savings” σε δισεκατομμύρια γαλονιών (billions of gallons) ήταν 40-26=14.
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