ANSWER

7-8 year olds

41424344454647484950  

51525354555657585960

61626364656667686970  

71727374757677787980  

81828384858687888990

As we see there are five “5” and five “0” so the answer is 5+5+5+5+5+0+0+0+0+0 =25

​

31323334353637383940

41424344454647484950

51525354555657585960

Adding what is left we get: 3+5+3+0+4+5+4+0+5+5 = 44.