Answer: 340 mm 
Given: 
Length of spider – 10 mm 
Length of guinea pig – 35 cm 
To solve the problem, we must first convert the length of the guinea pig in cm to mm. Since there are 10 mm in 1 cm, multiply 35 by 10 to get length of guinea pig in mm. 
35X10=350 mm 
Then, deduct 10 mm from 350 mm 
350-10 
340 mm 
The guinea pig Is longer than the spider by 340 mm.