Maths help! I am stuck on this question

Hi!

I am stuck on this question:

Intelligent life forms from the Alzir planetary system have a unique way of

dealing with foreign stellar visitors, a shrink ray. Alzirians of have been heard

saying “A shrunken problem is no problem at all”, often after a unlucky vis-

itor has been shrunk. Captain Kirk and his crew met a similar fate and after

the starship Enterprise and occupants where reduced by 87% of their origi-

nal size. After much diplomacy and explaining that the United Federation

of Planets were peaceful explorers, the Alzirians agreed to return them to

normal size. Fortunately by switching polarity the shrink ray becomes an

expansion ray. The return to normal size

(a) by what expansion factor would the Enterprise and crew need to un-

dergo?

(b) what would be the percentage increase required?

For part (a) of the question I know that since they shrunk by 87% they must 100% to start of by.

So now they are 100-87 = 13%. I don't know what I need to do next to find the expansion factor.

Do I do 100 divide by 13 = 7.69 and then it would be 7.69x100? I'm so lost!

Re: Maths help! I am stuck on this question

we need to expand them by E such that

$E * (0.13) = 1$ so

$E = \dfrac 1 {0.13} \approx 7.7$

$7.7 = 7.7 * 100\% = 770\%$

Re: Maths help! I am stuck on this question

Thank you so much!!!! @romsek