Answer:
140
Step-by-step explanation:
When working HCF and LCM problems, I like to think in terms of this little diagram:
(a [ b ) c]
It shows me one of the numbers is ab, the other is bc, the HCF is b and the LCM is abc. "a" and "c" must be relatively prime for "b" to be the HCF.
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Here, we're given ...
b = 20
ab = 320
abc = 2240
Then ...
c = abc/(ab) = 2240/320 = 7
x = bc = 20(7) . . . . . . equivalently, x = (abc·b)/(ab) = (2240·20)/320
x = 140
Replace the x with 2: f(2)=2*2+7=4+7=11
replace the x with 7: f(7)=2*7+7=14+7=21
Yes to both, and for future help, if you find a common denominator(the bottom one) by multiplication and one is higher, boom you have your answer.
