Answer:
23%; £80; 300; 4
Step-by-step explanation:
19. First, we'll work out what Rob earned on the telescope. That's[tex]176.2-(-242)=176.2+242=418.2[/tex] (£). Next we'll use the formula for profit %, profit over cost price, so that would be
[tex]\frac{418.2-340}{340}\\\\=\frac{78.2}{340}\\\\=0.23[/tex]
Which is 23%.
20. Let the original price be £[tex]x[/tex]. Then we have
[tex]x(1-15\%)=68\\x-0.15x=68\\0.85x=68\\x=80[/tex](£)
21. a) Let the original population be [tex]a[/tex] people. Then we have
[tex]a(1+20\%)=360\\a+0.2a=360\\1.2a=360\\a=300[/tex](people)
b) We'll assume that there are [tex]n[/tex] years before that happens. We know that the population grows by 60 each year, so
[tex]360+60n=600\\60n=240\\n=4[/tex](years)
