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3 years ago

If 5 times a number increased by 30 is 15, what is the number?

Mathematics

2 answers:

bija089 [108]3 years ago

7 0

Let's keep the,

Value of unknown number as y.

Then find the y,

→ 5y + 30 = 15

→ 5y = 15 - 30

→ 5y = -15

→ y = -15/5

→ [y = -3]

Therefore, -3 is the number.

weqwewe [10]3 years ago

3 0

Answer:

let x=the number

5x+30=15

5x=15-30

5x=-15

5x/5=-15/5

x=-3

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Suppose you toss a fair coin 10 times, let X denote the number of heads. (a) What is the probability that X=5? (b) What is the p

zubka84 [21]

Answer: The required answers are

(a) 0.25, (b) 0.62, (c) 6.

Step-by-step explanation: Given that we toss a fair coin 10 times and X denote the number of heads.

We are to find

(a) the probability that X=5

(b) the probability that X greater or equal than 5

(c) the minimum value of a such that P(X ≤ a) > 0.8.

We know that the probability of getting r heads out of n tosses in a toss of coin is given by the formula of binomial distribution as follows :

$P(X=r)=^nC_r\left(\dfrac{1}{2}\right)^r\left(\dfrac{1}{2}\right)^{n-r}.$

(a) The probability of getting 5 heads is given by

$P(X=5)\\\\\\=^{10}C_5\left(\dfrac{1}{2}\right)^5\left(\dfrac{1}{2}\right)^{10-5}\\\\\\=\dfrac{10!}{5!(10-5)!}\dfrac{1}{2^{10}}\\\\\\=0.24609\\\\\sim0.25.$

(b) The probability of getting 5 or more than 5 heads is

$P(X\geq 5)\\\\=P(X=5)+P(X=6)+P(X=7)+P(X=8)+P(X=9)+P(X=10)\\\\=^{10}C_5\left(\dfrac{1}{2}\right)^5\left(\dfrac{1}{2}\right)^{10-5}+^{10}C_6\left(\dfrac{1}{2}\right)^6\left(\dfrac{1}{2}\right)^{10-6}+^{10}C_7\left(\dfrac{1}{2}\right)^7\left(\dfrac{1}{2}\right)^{10-7}+^{10}C_8\left(\dfrac{1}{2}\right)^8\left(\dfrac{1}{2}\right)^{10-8}+^{10}C_9\left(\dfrac{1}{2}\right)^9\left(\dfrac{1}{2}\right)^{10-9}+^{10}C_{10}\left(\dfrac{1}{2}\right)^{10}\left(\dfrac{1}{2}\right)^{10-10}\\\\\\=0.24609+0.20507+0.11718+0.04394+0.0097+0.00097\\\\=0.62295\\\\\sim 0.62.$

(c) Proceeding as in parts (a) and (b), we see that

if a = 10, then

$P(X\leq 0)=0.00097,\\\\P(X\leq 1)=0.01067,\\\\P(X\leq 2)=0.05461,\\\\P(X\leq 3)=0.17179,\\\\P(X\leq 4)=0.37686,\\\\P(X\leq 5)=0.62295,\\\\P(X\leq 6)=0.82802.$

Therefore, the minimum value of a is 6.

Hence, all the questions are answered.

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3 years ago

If 3 to the power of x+1 = 81 and 81 to the power of x-y = 3 then what is the value of x and y?

fgiga [73]

From 1st condition:

3^(x+1)=81
Take log on both sides,
➡ log [3^(x+1)]=log81
Use the property: log(x^a)=a logx
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➡ (x+1) log 3=4×log 3
➡ (x+1)=4 (log 3 /log 3)
➡ x+1=4
➡ x=3➡↪➡↪ ANS

From 2nd condition, (Same process are repeated)

81^(x-y)=3
➡ 3^4(x-y)=3
➡ log [3^4(3-y)]=log 3
➡ 4(3-y) log 3=log 3
➡ (3-y)=(log 3)/(4log 3)
➡ 3-y=(1/4)
➡ y=11/4 ➡↪➡↪ ANS

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