Metamath Proof Explorer

Theorem 5t4e20

Description: 5 times 4 equals 20. (Contributed by Mario Carneiro, 19-Apr-2015) (Revised by AV, 6-Sep-2021)

Ref Expression
Assertion 5t4e20 
|- ( 5 x. 4 ) = ; 2 0

Proof

Step Hyp Ref Expression
1 5nn0 
 |-  5 e. NN0
2 3nn0 
 |-  3 e. NN0
3 df-4 
 |-  4 = ( 3 + 1 )
4 5t3e15 
 |-  ( 5 x. 3 ) = ; 1 5
5 1nn0 
 |-  1 e. NN0
6 eqid 
 |-  ; 1 5 = ; 1 5
7 1p1e2 
 |-  ( 1 + 1 ) = 2
8 5p5e10 
 |-  ( 5 + 5 ) = ; 1 0
9 5 1 1 6 7 8 decaddci2 
 |-  ( ; 1 5 + 5 ) = ; 2 0
10 1 2 3 4 9 4t3lem 
 |-  ( 5 x. 4 ) = ; 2 0