Answer:
The length of BC = 28 units
Step-by-step explanation:
* In triangle ABC
∵ Angles B and C are congruent
∴ m∠B = m∠C
* In any triangle if two angles are equal in measure, then the triangle is isosceles means the two sides which opposite to the congruent angles are equal in length
∴ AB = AC
∵ AB = 4x - 7
∵ AC = 2x + 7
∴ 4x - 7 = 2x + 7 ⇒ collect like terms
∴ 4x - 2x = 7 + 7
∴ 2x = 14 ⇒ divide both sides by 2
∴ x = 14 ÷ 2 = 7
* Now we can find the length of BC
∵ The length of BC = 4x ⇒ substitute the value of x
∴ The length of BC = 4 × 7 = 28 units
Answer:
she will drive a total of 886 miles
Step-by-step explanation:
C. First person -hellobrains
Answer:
512
Step-by-step explanation:
Suppose we ask how many subsets of {1,2,3,4,5} add up to a number ≥8. The crucial idea is that we partition the set into two parts; these two parts are called complements of each other. Obviously, the sum of the two parts must add up to 15. Exactly one of those parts is therefore ≥8. There must be at least one such part, because of the pigeonhole principle (specifically, two 7's are sufficient only to add up to 14). And if one part has sum ≥8, the other part—its complement—must have sum ≤15−8=7
.
For instance, if I divide the set into parts {1,2,4}
and {3,5}, the first part adds up to 7, and its complement adds up to 8
.
Once one makes that observation, the rest of the proof is straightforward. There are 25=32
different subsets of this set (including itself and the empty set). For each one, either its sum, or its complement's sum (but not both), must be ≥8. Since exactly half of the subsets have sum ≥8, the number of such subsets is 32/2, or 16.
