I don't quite understand the ten strategy, or what EXACTLY you're asking. But, what you can do is when you add a one digit number plus a nine, just change the nine to a ten and subtract one. It is very easy. So, 7+10 equals 17, subtract one and you get 16 which is 7+9. It is always one less than anything plus 10.
Answer: a) Unimodal and symmetric
b) 0.26
c) 0.038
Step-by-step explanation:
Given: Sample size of investors (n)= 131
True proportion of smartphone users(p) =26%
a) Since sampling distribution for the sample proportion is approximately normal when n is larger.
Normal distribution is Unimodal and symmetric.
So correct option : Unimodal and symmetric
b) mean of this sampling distribution = p = 0.26
c) standard deviation of the samplingdistribution = 
