Rounding / Convert To Percent

I have a question about rounding and converting to percentage and adding in the '%'..This is my original code

SELECT * FROM
( SELECT Baby,
CAST( CAST( SUM(TotalBaby) AS DECIMAL )/ CAST( SUM(TotalParent) AS DECIMAL) AS DECIMAL(10,4)) as BabyValue
FROM NewBorn
WHERE Category = 'Boy'

[code]....

But I also need my data to have the '%' and it should have 2 decimal place which is as below, I have tried to make it this way

CAST( CAST( SUM(TotalBaby) AS DECIMAL )/ CAST( SUM(TotalParent) AS DECIMAL) AS DECIMAL(10,4)) * 100 + '%' as BabyValue

But it prompt me the error 'Error converting data type varchar to numeric.'

A B C D
0.22%0.29%0.11%0.32%