Description Level D Learning Objectives Building on the addition skills up to +4 mastered in Level C, this level trains children in addition from 5 to 10 and addition involving larger numbers, with the goal of developing the essential mental math skills needed for calculation. Book (Volume/Month) — Week — Learning Content Book D1, Weeks 1–4 Addition +5: (1~9)+5, (1~14)+5, (1~19)+5 Addition +6: (1~9)+6, (1~13)+6, (1~19)+6 Achievement Test Book D2, Weeks 1–4 Addition +7: (1~9)+7, (1~19)+7, (1~23)+7 Addition +8: (1~9)+8, (1~19)+8, (1~22)+8 Achievement Test Book D3, Weeks 1–4 Addition +9: (1~9)+9, (1~15)+9, (1~21)+9 Addition +10: (1~9)+10, (1~15)+10, (1~20)+10 Achievement Test Book D4, Weeks 1–4 Comprehensive Addition +5~10: Numbers up to 19 + (5~6), Numbers up to 19 + (7~8) Numbers up to 19 + (9~10), Numbers up to 19 + (5~10) Addition with Larger Numbers Achievement Test Book D5, Weeks 1–4 Addition with Larger Numbers: Addition with sums of 15 or less Addition with sums of 20 or less Addition with sums of 25 or less Addition with sums of 30 or less Addition with sums of 35 or less Addition with sums of 40 or less Comprehensive Addition (Level D) Final Test