First term ,a=4 , common difference =4-7=-3, n =50
sum of first 50terms= (50/2)[2×4+(50-1)(-3)]
=25×[8+49]×-3
=25×57×-3
=25× -171
= -42925
derivation of the formula for the sum of n terms
Progression, S
S=a1+a2+a3+a4+...+an
S=a1+(a1+d)+(a1+2d)+(a1+3d)+...+[a1+(n−1)d] → Equation (1)
S=an+an−1+an−2+an−3+...+a1
S=an+(an−d)+(an−2d)+(an−3d)+...+[an−(n−1)d] → Equation (2)
Add Equations (1) and (2)
2S=(a1+an)+(a1+an)+(a1+an)+(a1+an)+...+(a1+an)
2S=n(a1+an)
S=n/2(a1+an)
Substitute an = a1 + (n - 1)d to the above equation, we have
S=n/2{a1+[a1+(n−1)d]}
S=n/2[2a1+(n−1)d]
It would take 630 seconds to boil the water.
Answer:
If it is an even number, then it is divisible by 2
Step-by-step explanation:
You flip the order of statements. One statement is "a number is divisible by 2", the other is "it is even" is the other.
Answer:
n = 6
Step-by-step explanation:
Two intersecting chords. The product of the parts of one chord is equal to the product of the parts of the other chord, that is
7(n + 4) = 5(n + 8) ← distribute parenthesis on both sides
7n + 28 = 5n + 40 ( subtract 5n from both sides )
2n + 28 = 40 ( subtract 28 from both sides )
2n = 12 ( divide both sides by 2 )
n = 6
Answer:
It is 185 mi to fort Worth van drives 2 hours at 65 mph how far will he be from fort Worth
Step-by-step explanation:
It is 185 mi to fort Worth van drives 2 hours at 65 mph how far will he be from fort Worth
