I'm not sure what your book is saying about the matter but a cell phone is not usually an essential expense. If it is saying it is though, it would be an essential flexible expense.
In Δ ABC, ∠A=120°, AB=AC=1
To draw a circumscribed circle Draw perpendicular bisectors of any of two sides.The point where these bisectors meet is the center of the circle.Mark the center as O.
Then join OA, OB, and OC.
Taking any one OA,OB and OC as radius draw the circumcircle.
Now, from O Draw OM⊥AB and ON⊥AC.
As chord AB and AC are equal,So OM and ON will also be equal.
The reason being that equal chords are equidistant from the center.
AM=MB=1/2 and AN=NC=1/2 [ perpendicular from the center to the chord bisects the chord.]
In Δ OMA and ΔONA
OM=ON [proved above]
OA is common.
MA=NA=1/2 [proved above]
ΔOMA≅ ONA [SSS]
∴ ∠OAN =∠OAM=60° [ CPCT]
In Δ OAN


OA=1
∴ OA=OB=OC=1, which is the radius of given Circumscribed circle.
We must calculate the lateral area which is given by:
A = (1/2) * pb * Ap
Where,
pb: perimeter of the base
Ap: Apotema
Calculating the apothem we have:
Ap = root ((646/2) ^ 2 + (350) ^ 2)
Ap = 476.27 feet
Calculating the perimeter of the base we have:
pb = 4 * (646)
pb = 2584 feet
Substituting values:
A = (1/2) * pb * Ap
A = (1/2) * (2584) * (476.27)
A = 615340.84 m ^ 2
Answer:
The minimum amount of glass used for the exterior is:
A = 615340.84 m ^ 2
Bus Bs route times will be:
45 mins
90 mins
135 mins
180 mins
Bus As times will be:
20 mins
40 mins
60 mins
...
180 mins.
Therefore 180 mins is the common factor, which is 9pm
Answer- since you are buying x packs of pencils, 2x packs of erasers, and 3x rolls of tape, you would be buying a total of 6x items.